Ownership Submission
FORM 3
 UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF 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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(Print or Type Responses)
1. Name and Address of Reporting Person *
  Font Juan
 2. Date of Event Requiring Statement (Month/Day/Year)
03/08/2018		 3. Issuer Name and Ticker or Trading Symbol
CoreSite Realty Corp [COR]
(Last)
(First)
(Middle)
C/O CORESITE REALTY CORPORATION, 1001 17TH STREET, SUITE 500		 4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director _____ 10% Owner
__X__ Officer (give title below) _____ Other (specify below)
SVP, General Management
 5. If Amendment, Date Original Filed(Month/Day/Year)
(Street)

DENVER, CO 80202		 6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Beneficially Owned
1.Title of Security
(Instr. 4)		 2. Amount of Securities Beneficially Owned
(Instr. 4)		 3. Ownership Form: Direct (D) or Indirect (I)
(Instr. 5)		 4. Nature of Indirect Beneficial Ownership
(Instr. 5)
Common Stock 12,412 (1) (2) (3)
D
 

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly. SEC 1473 (7-02)
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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 4)		 2. Date Exercisable and Expiration Date
(Month/Day/Year)		 3. Title and Amount of Securities Underlying Derivative Security
(Instr. 4)		 4. Conversion or Exercise Price of Derivative Security 5. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 5)		 6. Nature of Indirect Beneficial Ownership
(Instr. 5)
Date Exercisable Expiration Date Title Amount or Number of Shares
Stock Option (Right to Buy)   (4) 03/11/2021 Common Stock 1,250 $ 15.23 D  

Reporting Owners

Reporting Owner Name / Address Relationships
Director 10% Owner Officer Other
Font Juan
C/O CORESITE REALTY CORPORATION
1001 17TH STREET, SUITE 500
DENVER, CO 80202		       SVP, General Management  

Signatures

/s/ Derek S. McCandless, Attorney-in-Fact 03/19/2018
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 5(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) Includes 5,751 shares of unvested restricted stock awards granted to the reporting person under the issuer's 2010 Equity Incentive Award Plan. The unvested shares of restricted stock vest as follows: (i) 1,039 shares vest on March 3, 2019, (ii) 1,940 shares vest in two equal annual installments on March 2, 2019 and March 2, 2020, (iii) 2,310 shares vest in three equal annual installments on March 8, 2019, March 8, 2020 and March 8, 2021, and (iv) 462 shares vest in three equal installments on March 20, 2018, March 20, 2019 and March 20, 2020, in each case provided that the reporting person remains in continuous service with the issuer as of each vesting date.
(2) Includes 473 performance-based restricted shares ("PSAs") granted under the issuer's 2010 Equity Incentive Award Plan, all of which were granted in 2017.
(3) The number of PSAs earned is based on the issuer's achievement of relative total shareholder return ("TSR") measured versus the MSCI US REIT Index over a three-year performance period. The number of 2017 PSAs earned may range from 25% to 175% of target. The PSAs are earned as follows: (i) 20% of the PSAs are earned upon TSR achievement in year one of the performance period, (ii) 20% of the PSAs are earned upon TSR achievement in year two of the performance period, (iii) 20% of the PSAs are earned upon TSR achievement in year three of the performance period, and (iv) 40% of the PSAs are earned upon a cumulative TSR achievement over the three-year performance period, subject to the reporting person's continued service with the issuer at the end of the three-year performance period. The PSAs are granted and issued at the maximum percentage of the target amount.
(4) The stock options are fully vested.

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