FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person * SIMMONS HAROLD C   2. Issuer Name and Ticker or Trading Symbol KRONOS WORLDWIDE INC [KRO] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director __X__ 10% Owner __X__ Officer (give title below) _____ Other (specify below) Chairman of the Board (Last) (First) (Middle) 5430 LBJ FREEWAY, SUITE 1700 3. Date of Earliest Transaction (Month/Day/Year) 05/13/2011 (Street) DALLAS, TX 75240 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) ___ Form filed by One Reporting Person _X_ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock $0.01 par value 05/13/2011   J(1)   11,587 (2) A $ 53.7347 (2) 98,254 I by TFMC (3) Common Stock $0.01 par value 05/13/2011   J(1)   82,105 (4) A $ 54.8204 (4) 180,459 I by TFMC (3) Common Stock $0.01 par value 05/13/2011   J(1)   6,308 (5) A $ 55.3305 (5) 186,667 I by TFMC (3) Common Stock $0.01 par value               259,220 D   Common Stock $0.01 par value               28,995,021 I by Valhi (6) Common Stock $0.01 par value               17,609,635 I by NL (7) Common Stock $0.01 par value               54,856 I by Spouse (8) Common Stock $0.01 par value               2,686 I by Contran (9)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
SIMMONS HAROLD C 5430 LBJ FREEWAY, SUITE 1700 DALLAS, TX 75240	X	X	Chairman of the Board
CONTRAN CORP 5430 LBJ FREEWAY, SUITE 1700 DALLAS, TX 75240		X
VALHI INC /DE/ 5430 LBJ FREEWAY, SUITE 1700 DALLAS, TX 75240		X
VALHI HOLDING CO 5430 LBJ FREEWAY, SUITE 1700 DALLAS, TX 75240		X
DIXIE RICE AGRICULTURE CORP INC 5430 LBJ FREEWAY, SUITE 1700 DALLAS, TX 75240		X
TITANIUM METALS CORP 5430 LBJ FREEWAY, SUITE 1700 DALLAS, TX 75240		X
TIMET FINANCE MANAGEMENT CO 5430 LBJ FREEWAY, SUITE 1700 DALLAS, TX 75240		X
NL INDUSTRIES INC 5430 LBJ FREEWAY, SUITE 1700 DALLAS, TX 75240		X

Signatures

A. Andrew R. Louis. Attorney-in-fact, for Harold C. Simmons		05/16/2011
**Signature of Reporting Person		Date
A. Andrew R. Louis. Secretary, for Contran Corporation		05/16/2011
**Signature of Reporting Person		Date
A. Andrew R. Louis. Secretary, for Valhi, Inc.		05/16/2011
**Signature of Reporting Person		Date
A. Andrew R. Louis. Secretary, for Valhi Holding Corporation		05/16/2011
**Signature of Reporting Person		Date
A. Andrew R. Louis. Secretary, for Dixie Rice Agricultural Corporation, Inc.		05/16/2011
**Signature of Reporting Person		Date
A. Andrew R. Louis. Assistant Secretary, for Titanium Metals Corporation		05/16/2011
**Signature of Reporting Person		Date
A. Andrew R. Louis. Secretary, for NL Industries, Inc.		05/16/2011
**Signature of Reporting Person		Date
Gregory M. Swalwell. Vice President, for TIMET Finance Management Company		05/16/2011
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Open market purchase by TIMET Finance Management Company. See the Additional Information filed as Exhibit 99 to this statement for a description of the relationships among the persons joining in this filing.
(2)	The price reported in Column 4 is a weighted average price. These acquisitions involved 77 purchases at prices ranging from $53.20 to $54.17 per share. The reporting persons undertake to provide to the issuer, any security holder of the issuer or the U.S. Security and Exchange Commission, upon request, the full information regarding these purchases.
(3)	Directly held by TIMET Finance Management Company. See the Additional Information filed as Exhibit 99 to this statement for a description of the relationships among the persons joining in this filing.
(4)	The price reported in Column 4 is a weighted average price. These acquisitions involved 333 purchases at prices ranging from $54.25 to $55.24 per share. The reporting persons undertake to provide to the issuer, any security holder of the issuer or the U.S. Security and Exchange Commission, upon request, the full information regarding these purchases.
(5)	The price reported in Column 4 is a weighted average price. These acquisitions involved 45 purchases at prices ranging from $55.26 to $55.49 per share. The reporting persons undertake to provide to the issuer, any security holder of the issuer or the U.S. Security and Exchange Commission, upon request, the full information regarding these purchases.
(6)	Directly held by Valhi, Inc. See the Additional Information filed as Exhibit 99 to this statement for a description of the relationships among the persons joining in this filing.
(7)	Directly held by NL Industries, Inc. See the Additional Information filed as Exhibit 99 to this statement for a description of the relationship among the persons joining in this filing.
(8)	Directly held by the reporting person's wife. Mr. Simmons disclaims beneficial ownership of any shares of the issuer's common stock that his wife holds. See the Additional Information filed as Exhibit 99 to this statement for a description of the relationships among the persons joining in this filing.
(9)	Directly held by Contran Corporation. See the Additional Information filed as Exhibit 99 to this statement for a description of the relationship among the persons joining in this filing.
Remarks: Exhibit Index Exhibit 99 - Additional Information

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