On February 22, 2013, CoreSite Realty Corporation ("CoreSite") issued a press release reporting financial results and operating information for the quarter ended December 31, 2012. In addition, CoreSite made available on its website supplemental operating and financial data for the same period. The text of the press release and the supplemental information package are furnished herewith as Exhibits 99.1 and 99.2, respectively.

The information in this report, including Exhibits 99.1 and 99.2 attached hereto, shall not be deemed to be "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), or otherwise subject to the liabilities of that section, and shall not be incorporated by reference into any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such a filing.

(d) The following exhibits are furnished with this Current Report on Form 8-K.

Exhibit No.                                 Description

99.1           Press Release, dated February 22, 2013.

99.2           Quarter Ended December 31, 2012 Earnings Release and Supplemental
               Information, dated February 22, 2013.