FORM 11-K




                   (X) ANNUAL REPORT PURSUANT TO SECTION 15(d)
                     OF THE SECURITIES EXCHANGE ACT OF 1934

                   FOR THE FISCAL YEAR ENDED DECEMBER 31, 2001

                                       OR

                 ( ) TRANSITION REPORT PURSUANT TO SECTION 15(d)
                     OF THE SECURITIES EXCHANGE ACT OF 1934
                     For the transition period from ------ to ------

                          COMMISSION FILE NUMBER 1-3672









                               AMEREN CORPORATION
                      LONG-TERM SAVINGS PLAN - IUOE NO. 148



                           Issuer: Ameren Corporation


                              1901 Chouteau Avenue
                            St. Louis, Missouri 63103
                          (Principal Executive Office)






Ameren Corporation
Employee Long-Term
Savings Plan - IUOE No. 148
Report and Financial Statements
December 31, 2001 and 2000



Ameren Corporation
Employee Long-Term Savings Plan - IUOE No. 148

Index to Financial Statements
December 31, 2001 and 2000
--------------------------------------------------------------------------------

                                                                         Page

Report of Independent Accountants                                          1

Statement of Net Assets Available for Benefits
 at  December 31, 2001 and 2000                                            2

Statement of Changes in Net Assets Available for Benefits
 For the years ended December 31, 2001 and 2000                            3

Notes to Financial Statements                                           4-10














Note:  Schedules  required by 29 CFR  2520.103-10  of the  Department of Labor's
       Rules and Regulations for Reporting and Disclosure under ERISA have been
       omitted because they are not applicable.





                        Report of Independent Accountants


To the Participants and Administrator of
the Ameren Corporation
Employee Long-Term Savings Plan -
IUOE No. 148


In our opinion, the accompanying  statement of net assets available for benefits
and the  related  statement  of  changes in net assets  available  for  benefits
present fairly, in all material respects,  the net assets available for benefits
of the Ameren  Corporation  Employee  Long-Term Savings Plan - IUOE No. 148 (the
"Plan") at December 31, 2001 and 2000,  and the changes in net assets  available
for benefits for the years then ended in conformity with  accounting  principles
generally accepted in the United States of America.  These financial  statements
are the  responsibility  of the  Plan's  management;  our  responsibility  is to
express  an  opinion  on these  financial  statements  based on our  audits.  We
conducted our audits of these  statements in accordance with auditing  standards
generally  accepted in the United States of America,  which require that we plan
and perform the audit to obtain reasonable assurance about whether the financial
statements are free of material misstatement.  An audit includes examining, on a
test basis,  evidence  supporting  the amounts and  disclosures in the financial
statements,  assessing the accounting  principles used and significant estimates
made by management, and evaluating the overall financial statement presentation.
We believe that our audits provide a reasonable basis for our opinion.



/s/ PricewaterhouseCoopers LLP

PricewaterhouseCoopers LLP
St. Louis, Missouri
June 27, 2002



Ameren Corporation
Employee Long-Term Savings Plan - IUOE No. 148

Statement of Net Assets Available for Benefits
December 31, 2001 and 2000
--------------------------------------------------------------------------------
                                                    2001                2000

Investments in Central Illinois Public Service
 Company Master Long-Term Savings Trust         $ 25,810,594        $ 27,924,640

Cash                                                   2,161              10,613

Receivables:
    Participant contributions                         88,152              81,434
    Employer contributions                            16,880               3,812
    Dividends and interest                            19,559              17,836
    Due from broker for securities sold              139,320             252,074
                                            ----------------   -----------------

Net assets available for benefits                $26,076,666         $28,290,409
                                            ================   =================















    The accompanying notes are an integral part of the financial statements.

                                       -2-





Ameren Corporation
Employee Long-Term Savings Plan - IUOE No. 148

Statement of Changes in Net Assets Available for Benefits
For the Years Ended December 31, 2001 and 2000
--------------------------------------------------------------------------------


                                                                              For the year ended December 31,
                                                                                  2001               2000
                                                                                  ----               ----
                                                                                      
Investment (loss) income:
    Interest and dividends                                                     $  922,029        $ 1,112,311
    Net (depreciation) appreciation in fair value of investments               (2,780,929)         1,482,281
                                                                          ----------------   ----------------

                                                                               (1,858,900)         2,594,592
                                                                          ----------------   ----------------

Participant contributions                                                       1,561,151          1,530,325
Employer contributions                                                            184,110             36,866
                                                                          ----------------   ----------------

                                                                                1,745,261          1,567,191
                                                                          ----------------   ----------------

Benefits paid to participants                                                   2,098,064          1,997,281
Administrative expenses                                                             2,040              2,001
                                                                          ----------------   ----------------

                                                                                2,100,104          1,999,282
                                                                          ----------------   ----------------

Net (decrease) increase                                                        (2,213,743)         2,162,501

Net assets available for benefits:
    Beginning of the year                                                      28,290,409         26,127,908
                                                                          ----------------   ----------------

    End of the year                                                           $26,076,666        $28,290,409
                                                                          ================   ================












    The accompanying notes are an integral part of the financial statements.

                                      -3-



Ameren Corporation
Employee Long-Term Savings Plan - IUOE No. 148

Notes to Financial Statements
For the Year Ended December 31, 2001 and 2000
--------------------------------------------------------------------------------

1.   Description of the Plan

     General
     The  following is a brief  summary of the various  provisions of the Ameren
     Corporation (the Company)  Employee  Long-Term  Savings Plan - IUOE No. 148
     (the Plan). The Plan provides for the investment in certain funds under the
     Plan for each  participating  employee (the  Participant)  of  AmerenEnergy
     Generating  Company,  an indirectly  wholly owned subsidiary of the Company
     (Participating  Subsidiaries).   Participants  should  refer  to  the  Plan
     document for more complete information.

     The Plan initially was  established as the Central  Illinois Public Service
     Company Employee  Long-Term Savings Plan - IUOE No. 148.  Effective January
     1, 2000,  the Plan was renamed the Ameren  Corporation  Employee  Long-Term
     Savings Plan - IUOE No. 148.

     The Company  adopted the Plan on  January 1,  1990, to provide a systematic
     means by which  certain  eligible  employees  of the  Company  may  adopt a
     regular  savings  program and secure federal income tax benefits  resulting
     from  participation  in the Plan. The Plan is a defined  contribution  plan
     subject to the Employee Retirement Income Security Act of 1974 (ERISA).

     The  Company  serves as sponsor  of the Plan,  and,  consequently,  has the
     authority to amend or terminate  the Plan subject to certain  restrictions.
     The Board of Directors of the Company has the authority and  responsibility
     for the general  administration of the Plan. Merrill Lynch Trust Company of
     America,  as Trustee,  has the  authority  and  responsibility  to hold and
     protect the assets of the Plan in accordance  with Plan  provisions and the
     separate Trust Agreement.

     Effective  December  2001,  when  dividends  are paid on shares of  Company
     common stock held in the Ameren Stock Fund, these dividends  purchase newly
     issued shares of Ameren common stock at fair market value instead of Ameren
     shares being purchased in the open market.

     Participation
     Each employee of the Participating Subsidiaries receiving regular salary or
     wages who is part of the IUOE Local No. 148 collective  bargaining unit and
     who has  both  completed  one year of  service  (defined  as a  consecutive
     twelve-month period beginning with his/her employment  commencement date or
     anniversary  thereof during which he/she has completed at least 1,000 hours
     of service)  and has attained the age of 21 is eligible to become an active
     participant.

     Contributions
     Participants  may contribute  from 1% to 15% of their base  compensation to
     the Plan through payroll deductions (basic  contributions).  Effective June
     1, 2001, the Company makes a matching  contribution  equal to $.25 for each
     $1.00  on  the  first  6%  of a  participant's  contribution  (basic  match
     contribution).  The Company will  contribute  an  additional  $.05 for each
     $1.00 on the first 6% of a participant's contribution to be invested in the
     Ameren Common Stock Fund (additional matching  contribution).  For contract
     employees,  Company  matching  contributions  are made  based  on  specific
     agreements  between the Company and the  individual  collective  bargaining
     unit. A portion of Company matching contributions is invested in the Ameren
     Common  Stock  Fund.  All  Company  contributions  are  made to the  extent
     sufficient earnings are available.

                                      -4-




Ameren Corporation
Employee Long-Term Savings Plan - IUOE No. 148

Notes to Financial Statements
For the Year Ended December 31, 2001 and 2000
--------------------------------------------------------------------------------

     Participants  direct  their basic  contributions  and the  Company's  basic
     matching  contributions by electing that such  contributions be placed in a
     single  investment fund or allocated in increments of 1% to any combination
     of investment funds.  Such fund allocation  elections may be changed daily.
     Earnings  derived from the assets of any investment  fund are reinvested in
     the fund to which they relate.  Participants  may elect daily to reallocate
     all or in 1% increments, the value of their accounts between funds. Pending
     investment  of the  assets  into  any  investment  fund,  the  Trustee  may
     temporarily make certain short-term investments.

     Vesting
     The amounts in Participants' accounts, including Company contributions, are
     fully vested at all times.

     Participant Loans
     The Plan  permits  Participants  to borrow from their  accounts  within the
     Plan. Such borrowings may be made subject to the following: (1) the minimum
     amount of the loan is $500,  (2) the  amount of the loan may not exceed the
     lesser  of  $50,000  or  fifty   percent  of  the  vested   amount  in  the
     participant's  account,  (3) the loan will bear a fixed  interest  rate and
     repayments  will  be made  through  mutual  agreement  subject  to  certain
     statutory  repayment time limits,  and (4) such other rules and regulations
     as may be  adopted by the  Company.  At  December  31,  2001 and 2000,  the
     interest rates on participant loans ranged from 5% to 9.5%.

     Payment of Benefits
     Upon  termination  of  employment  for any reason,  a  Participant  will be
     entitled  to receive  the  balance in the  Participant's  account  less the
     unpaid  amount  of  any  outstanding  loan  (including  accrued  interest).
     Generally,  distributions  will be made in a lump sum; however,  in certain
     circumstances a Participant may also elect to receive his/her  distribution
     in installments.  Certain distributions may be deferred until a participant
     reaches  age 70 1/2, dies, or requests an earlier  distribution  (whichever
     occurs first).

     Amounts that have been requested for withdrawal by  Participants,  but have
     not yet been  distributed by the Plan, are included in net assets available
     for  benefits.   There  were  no  amounts   requested  for   withdrawal  by
     Participants,  but not yet distributed by the Plan, as of December 31, 2001
     or 2000.

     Plan Termination
     The Company has a right to  terminate  the Plan at any time  subject to the
     provisions of ERISA. Upon  termination,  the Trustee will distribute assets
     remaining in the Trust Fund with the exception that no distributions  shall
     be made until a participant attains age 59 1/2, except in certain specified
     situations.




                                      -5-




Ameren Corporation
Employee Long-Term Savings Plan - IUOE No. 148

Notes to Financial Statements
For the Year Ended December 31, 2001 and 2000
--------------------------------------------------------------------------------

2.   Summary of Significant Accounting Policies

     Basis of Accounting
     The  financial  statements of the Plan are prepared on the accrual basis of
     accounting.

     Use of Estimates
     The  preparation  of financial  statements  in conformity  with  accounting
     principles  generally  accepted  in the United  States of America  requires
     management  to make  estimates  and  assumptions  that affect the  reported
     amounts of assets and liabilities  and disclosure of contingent  assets and
     liabilities  at the  date of the  financial  statements  and  the  reported
     amounts  of  changes  in net  assets  available  for  benefits  during  the
     reporting period. Actual results could differ from those estimates.

     Investments
     All  investments  are  presented  at fair value as of December 31, 2001 and
     2000. The fair value of the Ameren Common Stock Fund was  determined  using
     year-end  published  market prices.  Investments  in equity  securities and
     bonds are valued at net asset market value including  accrued income on the
     last  business day of each year.  Investments  in the Money Market Fund and
     Merrill Lynch Retirement Preservation Trust are valued at cost plus accrued
     income,  which approximates  market.  Participant loans are valued at cost,
     which approximates fair market value.

     Investment  securities are exposed to various risks, such as interest rate,
     market,  and  credit.  Due to the  level of risk  associated  with  certain
     investment  securities and the level of  uncertainty  related to changes in
     the value of investment securities, it is at least reasonably possible that
     changes  in risks in the near term  could  materially  affect  the  amounts
     reported in the Statement of Net Assets Available for Benefits.

     Income
     Interest  income is  recorded  on the  accrual  basis.  Dividend  income is
     recorded on the ex-dividend date.

     Gains and losses on security  transactions  are recorded on the trade date.
     Net unrealized  appreciation or  depreciation  for the year is reflected in
     net appreciation  (depreciation) of investments on the Statement of Changes
     in Net Assets Available for Benefits.

     Expenses
     In general, expenses to administer the Plan, including fees and expenses of
     the Trustee,  are paid by the Company,  except as provided for in the Plan.
     All transaction fees of an investment fund are paid from the assets of that
     investment fund.

     Benefit Payments
     Benefit payments are recorded when paid.




                                      -6-




Ameren Corporation
Employee Long-Term Savings Plan - IUOE No. 148

Notes to Financial Statements
For the Year Ended December 31, 2001 and 2000
--------------------------------------------------------------------------------

3.   Transactions with Parties-in-Interest

     At December  31, 2001,  the Plan held Company  common stock with a cost and
     market value of $7,565,628 and $9,379,124,  respectively.  During 2001, the
     Plan purchased shares at a cost of $2,294,670 and sold shares at $1,133,635
     resulting in a net realized  gain of  $140,636.  The Plan also  distributed
     shares value at $538,702 to persons withdrawing from the Plan.

     At December  31, 2000,  the Plan held Company  common stock with a cost and
     market value of $6,486,748 and $9,232,626,  respectively.  During 2000, the
     Plan  purchased  shares at a cost of  $1,866,191  and sold shares valued at
     $5,351,525,  resulting  in a net realized  gain of $636,300.  The Plan also
     distributed shares valued at $621,872 to persons withdrawing from the Plan.

     At December 31, 2001, the Plan held  investments  in various  accounts that
     are related to Merrill  Lynch,  the Plan's  trustee.  At December 31, 2001,
     these investments had a cost and market value of $6,467,146 and $7,534,911,
     respectively. At December 31, 2000, these investments had a cost and market
     value of $6,374,529 and $8,423,087, respectively.

     These  transactions  are  allowable  party-in-interest  transactions  under
     Section 408(b)(8) of the ERISA regulations.

4.   Nonparticipant-Directed Investments

     Information  about the net assets  and the  significant  components  of the
     changes in net assets relating to the  nonparticipant-directed  investments
     is as follows:

                                                          December 31,
                                                              2001
Net assets:
    Ameren Common Stock Fund                                $  23,871

Changes in net assets:
    Dividends                                                     458
    Net appreciation in fair value of investments                 966
    Employer contributions                                     22,447










                                      -7-



Ameren Corporation
Employee Long-Term Savings Plan - IUOE No. 148

Notes to Financial Statements
For the Year Ended December 31, 2001 and 2000
--------------------------------------------------------------------------------

5.   Federal Income Tax Status

     The Plan is  designed  to  qualify as a  deferred  compensation  plan under
     sections  401(a)  and  401(k)  of  the  Internal   Revenue  Code  of  1986.
     Qualification  of the Plan means that a Participant  will not be subject to
     federal income taxes on amounts  contributed to the Participant's  account,
     or the earnings or  appreciation  thereon,  until such  amounts  either are
     withdrawn by the  Participant or are  distributed  to the  Participant or a
     beneficiary  in the event of the  Participant's  death.  Payroll  reduction
     contributions  to a  Participant's  account  reduce the gross income of the
     Participant   for  federal  income  tax  purposes  to  the  extent  of  the
     contributions.  The Company received a favorable  determination letter from
     the  Internal  Revenue  Service  dated  August  20,  1996,  concerning  the
     qualification  of  the  Plan  under  federal  income  tax  regulations.  In
     addition,  the Company also received a favorable  determination letter from
     the  Internal   Revenue   Service  dated   December  8,  1986,   concerning
     qualification  of the Master  Long-Term  Savings Trust under federal income
     tax regulations.  Management  believes that the Plan is currently  designed
     and is being  operated in  compliance  with  requirements  of the  Internal
     Revenue Code and that the Plan is tax exempt as of the financial  statement
     date. See also Note 6.

     Discussions of the federal income tax  consequences of the Plan,  including
     consequences on distributions of a Participant's  account, are contained in
     the Company's Employee Long-Term Savings Plan Summary Plan Description.

6.   Participation in Master Trust

     The Central Illinois Public Service Company Master Long-Term  Savings Trust
     (the Master Trust) was  established  April 1, 1985, to serve as the funding
     medium for the Plan and for the other separate  Employee  Long-Term Savings
     Plan which is for the  members of the IBEW No.  702  collective  bargaining
     unit employed by the Participating Subsidiaries.  This separate plan is not
     included  in this  report and is shown  separately  in its own  report.  At
     December  31, 2001 and 2000,  the Plan's  interest in the net assets of the
     master trust was approximately 43% and 44%, respectively.















                                      -8-






Ameren Corporation
Employee Long-Term Savings Plan - IUOE No. 148

Notes to Financial Statements
For the Year Ended December 31, 2001 and 2000
--------------------------------------------------------------------------------

  The Master  Trusts'  Statement  of Net Assets at December 31, 2001 and 2000
  and Statement of Changes in Net Assets for the Year Ended December 31, 2001
  and 2000 are included below:

                      Statement of Net Assets, Master Trust


                                                                              December 31,
                                                                         2001              2000
                                                                               
Assets
    Investments at fair value:
      Ameren Common Stock Fund                                      $ 19,523,224      $ 19,292,555
      Bond Index Fund                                                  2,320,320         1,753,203
      Money Market Fund                                                4,943,113         5,151,053
      Growth Equity Fund                                               8,181,620        11,017,606
      Standard & Poor's 500 Equity Index Trust                        13,657,281        15,027,531
      Merrill Lynch Retirement Preservation Trust                      2,448,659         2,549,312
      AIM Value Fund                                                   4,729,651         4,585,338
      Merrill Lynch Global Allocation Fund - Class A                     949,058           847,694
      Merrill Lynch Capital Fund - Class A                               846,394           850,298
      Participant Loan Fund                                            2,585,358         2,705,672

Cash                                                                       4,442            36,663

Receivables:
    Participant contributions                                            262,042           240,309
    Employer contributions                                                40,087            20,618
    Dividends and interest                                                41,704            37,830
    Due from broker for securities sold                                  139,320           257,905
                                                                ----------------  ----------------

Net assets available for benefits                                   $ 60,672,273      $ 64,373,587
                                                                ================  ================











                                      -9-





Ameren Corporation
Employee Long-Term Savings Plan - IUOE No. 148

Notes to Financial Statements
For the Years Ended December 31, 2001 and 2000
--------------------------------------------------------------------------------

                Statement of Changes in Net Assets, Master Trust


                                                                      For the year ended December 31,
                                                                         2001                  2000
                                                                                  
Investment (loss) income:
     Interest and dividends                                            $1,834,557            $2,395,414
     Net appreciation (depreciation) in fair value of investments      (7,186,188)              827,966
                                                                   ---------------      ---------------

                                                                       (5,351,631)            3,223,380
                                                                   ---------------      ---------------

Participant contributions                                               4,949,114             5,107,076
Employer contributions                                                    590,373               334,939
                                                                   ---------------      ---------------

                                                                        5,539,487             5,442,015
                                                                   ---------------      ---------------

Benefits paid to participants                                           3,883,231             4,250,519
Administrative expenses                                                     5,939                 6,640
                                                                   ---------------      ---------------

                                                                        3,889,170             4,257,159
                                                                   ---------------      ---------------

Net (decrease) increase                                                (3,701,314)            4,408,236

Net assets available for benefits:
     Beginning of the year                                              64,373,587            59,965,351
                                                                   ---------------      ---------------

     End of the year                                                  $ 60,672,273          $ 64,373,587
                                                                   ===============      ================




7.   Subsequent Events

     Effective  June 1, 2002,  with the passage of the  Economic  Growth and Tax
     Relief  Reconciliation Act (EGTRRP),  the Plan was changed to designate the
     Ameren Stock Fund of the Plan as an Employee  Stock  Ownership  Plan and to
     allow all employees a choice  between  dividend  reinvestment  and dividend
     payment  on  their  various   Employee   Stock   Ownership  Plan  accounts.
     Additionally,  employees  age 55 and older  will be able to  diversify  the
     additional  Company match portion of the Ameren Stock Fund.  Effective July
     1,  2002,  the  "catch  up"  contribution  provision  of  (EGTRRP)  for all
     employees age 50 and older was implemented as well.

     The Plan obtained a favorable  determination  letter May 29, 2002, in which
     the Internal  Revenue Service stated,  that the Plan was in compliance with
     the applicable requirements of the Internal Revenue Code.



                                      -10-





     The Plan.  Pursuant to the  requirements of the Securities  Exchange Act of

1934,  the  registrant  has duly caused  this annual  report to be signed on its

behalf by the undersigned hereunto duly authorized.




                                          AMEREN CORPORATION
                                          LONG-TERM SAVINGS
                                          PLAN - IUOE NO. 148


                                          AMEREN SERVICES COMPANY
                                              (Administrator)




                                          By        /s/ Donna K. Martin
                                              ---------------------------------
                                                        Donna K. Martin
                                                        Vice President

June 28, 2002




                                  EXHIBIT INDEX

                             Exhibits Filed Herewith
                             -----------------------


Exhibit No.                         Description
-----------             --------------------------------------
    23                  Consent of Independent Accountants















                                      -11-





                                                                      EXHIBIT 23



                       CONSENT OF INDEPENDENT ACCOUNTANTS


We  hereby  consent  to the  incorporation  by  reference  in  the  Registration
Statement on Form S-8 (No.  333-43743) of Ameren Corporation of our report dated
June 27, 2002  relating to the financial  statements  of the Ameren  Corporation
Employee Long-Term Savings Plan-IUOE No. 148, which appears in this Form 11-K.




/s/ PricewaterhouseCoopers LLP

PricewaterhouseCoopersLLP
St. Louis, Missouri
June 27, 2002