<html>
<head>

  </head>
<body lang="EN-US">
<div>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">&nbsp;</font></b></p>
<div style="border:none;border-top:solid windowtext 1.5pt;padding:1.0pt 0in 0in 0in;">
<p align="center" style="border:none;margin:0in 0in .0001pt;padding:0in;text-align:center;"><b><font size="1" face="Times New Roman" style="font-size:2.0pt;font-weight:bold;">&nbsp;</font></b></p>
</div>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="4" face="Times New Roman" style="font-size:14.5pt;font-weight:bold;">UNITED STATES</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="4" face="Times New Roman" style="font-size:14.5pt;font-weight:bold;">SECURITIES AND EXCHANGE COMMISSION</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Washington, D.C. 20549</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="3" face="Times New Roman" style="font-size:12.0pt;">&nbsp;</font></p>
<div style="border:none;border-top:solid windowtext 1.5pt;padding:1.0pt 0in 0in 0in;">
<p align="center" style="border:none;margin:0in 0in .0001pt;padding:0in;text-align:center;"><font size="1" face="Times New Roman" style="font-size:3.0pt;">&nbsp;</font></p>
</div>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="4" face="Times New Roman" style="font-size:14.5pt;font-weight:bold;">FORM&nbsp;8-K</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="3" face="Times New Roman" style="font-size:12.0pt;">&nbsp;</font></p>
<div style="border:none;border-top:solid windowtext 1.5pt;padding:1.0pt 0in 0in 0in;">
<p align="center" style="border:none;margin:0in 0in .0001pt;padding:0in;text-align:center;"><font size="1" face="Times New Roman" style="font-size:3.0pt;">&nbsp;</font></p>
</div>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="4" face="Times New Roman" style="font-size:14.0pt;font-weight:bold;">CURRENT REPORT</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="1" face="Times New Roman" style="font-size:6.0pt;">&nbsp;</font></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Pursuant to Section&nbsp;13 OR 15(d)&nbsp;of The</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Securities Exchange Act of 1934</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Date of Report (Date of earliest event reported): July 25, 2013</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="4" face="Times New Roman" style="font-size:14.0pt;">&nbsp;</font></p>
<div style="border:none;border-top:solid windowtext 1.5pt;padding:1.0pt 0in 0in 0in;">
<p align="center" style="border:none;margin:0in 0in .0001pt;padding:0in;text-align:center;"><font size="1" face="Times New Roman" style="font-size:6.0pt;">&nbsp;</font></p>
</div>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="5" face="Times New Roman" style="font-size:16.0pt;font-weight:bold;">CoreSite Realty Corporation</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="1" face="Times New Roman" style="font-size:8.5pt;font-weight:bold;">(Exact name of registrant as specified in its charter)</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="4" face="Times New Roman" style="font-size:14.0pt;">&nbsp;</font></p>
<div style="border:none;border-top:solid windowtext 1.5pt;padding:1.0pt 0in 0in 0in;">
<p align="center" style="border:none;margin:0in 0in .0001pt;padding:0in;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p align="center" style="border:none;margin:0in 0in .0001pt;padding:0in;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
</div>
<div align="right">
<table border="0" cellspacing="0" cellpadding="0" width="100%" style="border-collapse:collapse;width:100.0%;">
<tr>
<td width="32%" valign="top" style="padding:0in 0in 0in 0in;width:32.0%;">
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="1" face="Times New Roman" style="font-size:8.5pt;font-weight:bold;">Maryland</font></b></p>    </td>
<td width="2%" valign="bottom" style="padding:0in 0in 0in 0in;width:2.0%;">
<p style="margin:0in 0in .0001pt;"><b><font size="1" face="Times New Roman" style="font-size:1.0pt;font-weight:bold;">&nbsp;</font></b></p>    </td>
<td width="32%" valign="top" style="padding:0in 0in 0in 0in;width:32.0%;">
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="1" face="Times New Roman" style="font-size:8.5pt;font-weight:bold;">001-34877</font></b></p>    </td>
<td width="2%" valign="bottom" style="padding:0in 0in 0in 0in;width:2.0%;">
<p style="margin:0in 0in .0001pt;"><b><font size="1" face="Times New Roman" style="font-size:1.0pt;font-weight:bold;">&nbsp;</font></b></p>    </td>
<td width="32%" valign="top" style="padding:0in 0in 0in 0in;width:32.0%;">
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="1" face="Times New Roman" style="font-size:8.5pt;font-weight:bold;">27-1925611</font></b></p>    </td>   </tr>
<tr>
<td width="32%" valign="top" style="padding:0in 0in 0in 0in;width:32.0%;">
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="1" face="Times New Roman" style="font-size:7.0pt;font-weight:bold;">(State   or other jurisdiction<br>   of incorporation)</font></b></p>    </td>
<td width="2%" valign="bottom" style="padding:0in 0in 0in 0in;width:2.0%;">
<p style="margin:0in 0in .0001pt;"><b><font size="1" face="Times New Roman" style="font-size:1.0pt;font-weight:bold;">&nbsp;</font></b></p>    </td>
<td width="32%" valign="top" style="padding:0in 0in 0in 0in;width:32.0%;">
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="1" face="Times New Roman" style="font-size:7.0pt;font-weight:bold;">(Commission<br>   File Number)</font></b></p>    </td>
<td width="2%" valign="bottom" style="padding:0in 0in 0in 0in;width:2.0%;">
<p style="margin:0in 0in .0001pt;"><b><font size="1" face="Times New Roman" style="font-size:1.0pt;font-weight:bold;">&nbsp;</font></b></p>    </td>
<td width="32%" valign="top" style="padding:0in 0in 0in 0in;width:32.0%;">
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="1" face="Times New Roman" style="font-size:7.0pt;font-weight:bold;">(IRS   Employer<br>   Identification No.)</font></b></p>    </td>   </tr>
<tr>
<td width="32%" valign="top" style="padding:0in 0in 0in 0in;width:32.0%;">
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>    </td>
<td width="2%" valign="bottom" style="padding:0in 0in 0in 0in;width:2.0%;">
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>    </td>
<td width="32%" valign="top" style="padding:0in 0in 0in 0in;width:32.0%;">
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>    </td>
<td width="2%" valign="bottom" style="padding:0in 0in 0in 0in;width:2.0%;">
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>    </td>
<td width="32%" valign="top" style="padding:0in 0in 0in 0in;width:32.0%;">
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>    </td>   </tr>
<tr>
<td width="66%" colspan="3" valign="top" style="padding:0in 0in 0in 0in;width:66.0%;">
<p align="center" style="margin:0in 0in .0001pt 10.1pt;text-align:center;text-indent:-10.1pt;"><b><font size="1" face="Times New Roman" style="font-size:8.5pt;font-weight:bold;">1050 17th Street, Suite&nbsp;800<br>   Denver, CO</font></b></p>    </td>
<td width="2%" valign="bottom" style="padding:0in 0in 0in 0in;width:2.0%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>    </td>
<td width="32%" valign="bottom" style="padding:0in 0in 0in 0in;width:32.0%;">
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="1" face="Times New Roman" style="font-size:8.5pt;font-weight:bold;">80265</font></b></p>    </td>   </tr>
<tr>
<td width="66%" colspan="3" valign="top" style="padding:0in 0in 0in 0in;width:66.0%;">
<p align="center" style="margin:0in 0in .0001pt 10.1pt;text-align:center;text-indent:-10.1pt;"><b><font size="1" face="Times New Roman" style="font-size:7.0pt;font-weight:bold;">(Address of principal executive   offices)</font></b></p>    </td>
<td width="2%" valign="bottom" style="padding:0in 0in 0in 0in;width:2.0%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>    </td>
<td width="32%" valign="top" style="padding:0in 0in 0in 0in;width:32.0%;">
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="1" face="Times New Roman" style="font-size:7.0pt;font-weight:bold;">(Zip   Code)</font></b></p>    </td>   </tr>  </table>
</div>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="1" face="Times New Roman" style="font-size:8.5pt;font-weight:bold;">Registrant&#146;s telephone number, including area code: (866)&nbsp;777-2673</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="1" face="Times New Roman" style="font-size:8.5pt;font-weight:bold;">N/A</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="1" face="Times New Roman" style="font-size:7.0pt;font-weight:bold;">(Former name or former address, if changed since last report.)</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="1" face="Times New Roman" style="font-size:5.0pt;">&nbsp;</font></p>
<div style="border:none;border-top:solid windowtext 1.5pt;padding:1.0pt 0in 0in 0in;">
<p align="center" style="border:none;margin:0in 0in .0001pt;padding:0in;text-align:center;"><font size="1" face="Times New Roman" style="font-size:5.0pt;">&nbsp;</font></p>
</div>
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">Check the appropriate box below if the Form&nbsp;8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:</font></p>
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:4.0pt;">&nbsp;</font></p>
<table border="0" cellspacing="0" cellpadding="0" width="100%" style="border-collapse:collapse;width:100.0%;">
<tr>
<td width="2%" valign="top" style="padding:0in 0in 0in 0in;width:2.92%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Wingdings" style="font-size:8.5pt;">o</font></p>    </td>
<td width="97%" valign="bottom" style="padding:0in 0in 0in 0in;width:97.08%;">
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">Written   communications pursuant to Rule&nbsp;425 under the Securities Act (17 CFR   230.425)</font></p>    </td>   </tr>
<tr>
<td width="2%" valign="top" style="padding:0in 0in 0in 0in;width:2.92%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:7.5pt;">&nbsp;</font></p>    </td>
<td width="97%" valign="bottom" style="padding:0in 0in 0in 0in;width:97.08%;">
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="1" face="Times New Roman" style="font-size:7.5pt;">&nbsp;</font></p>    </td>   </tr>
<tr>
<td width="2%" valign="top" style="padding:0in 0in 0in 0in;width:2.92%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Wingdings" style="font-size:8.5pt;">o</font></p>    </td>
<td width="97%" valign="bottom" style="padding:0in 0in 0in 0in;width:97.08%;">
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">Soliciting   material pursuant to Rule&nbsp;14a-12 under the Exchange Act (17 CFR   240.14a-12)</font></p>    </td>   </tr>
<tr>
<td width="2%" valign="top" style="padding:0in 0in 0in 0in;width:2.92%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:7.5pt;">&nbsp;</font></p>    </td>
<td width="97%" valign="bottom" style="padding:0in 0in 0in 0in;width:97.08%;">
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="1" face="Times New Roman" style="font-size:7.5pt;">&nbsp;</font></p>    </td>   </tr>
<tr>
<td width="2%" valign="top" style="padding:0in 0in 0in 0in;width:2.92%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Wingdings" style="font-size:8.5pt;">o</font></p>    </td>
<td width="97%" valign="bottom" style="padding:0in 0in 0in 0in;width:97.08%;">
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">Pre-commencement   communications pursuant to Rule&nbsp;14d-2(b)&nbsp;under the Exchange Act (17   CFR 240.14d-2(b))</font></p>    </td>   </tr>
<tr>
<td width="2%" valign="top" style="padding:0in 0in 0in 0in;width:2.92%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:7.5pt;">&nbsp;</font></p>    </td>
<td width="97%" valign="bottom" style="padding:0in 0in 0in 0in;width:97.08%;">
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="1" face="Times New Roman" style="font-size:7.5pt;">&nbsp;</font></p>    </td>   </tr>
<tr>
<td width="2%" valign="top" style="padding:0in 0in 0in 0in;width:2.92%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Wingdings" style="font-size:8.5pt;">o</font></p>    </td>
<td width="97%" valign="bottom" style="padding:0in 0in 0in 0in;width:97.08%;">
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">Pre-commencement   communications pursuant to Rule&nbsp;13e-4(c)&nbsp;under the Exchange Act (17   CFR 240.13e-4(c))</font></p>    </td>   </tr>  </table>
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<div style="border:none;border-top:solid windowtext 1.5pt;padding:1.0pt 0in 0in 0in;">
<p style="border:none;margin:0in 0in .0001pt;padding:0in;"><font size="1" face="Times New Roman" style="font-size:5.0pt;">&nbsp;</font></p>
</div>
<div style="margin:0in 0in .0001pt;"><hr size="3" width="100%" noshade color="#010101" align="left"></div>
</div>
<!-- SEQ.=1,FOLIO='',FILE='C:\JMS\pselva\13-17055-1\task6148723\17055-1-ba.htm',USER='105344',CD='Jul 24 22:18 2013' -->

<br clear="all" style="page-break-before:always;">
<div>
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="1" face="Times New Roman" style="font-size:8.5pt;font-weight:bold;">Section&nbsp;2 &#151; Financial Information</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;"><b><font size="1" face="Times New Roman" style="font-size:8.5pt;font-weight:bold;">Item&nbsp;2.02 Results of Operations and Financial Condition.</font></b></p>
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:5.0pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">On July 25, 2013, CoreSite Realty Corporation (&#147;CoreSite&#148;) issued a press release reporting financial results and operating information for the quarter ended June 30, 2013. 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.</font></p>
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">The information in this report, including Exhibits 99.1 and 99.2 attached hereto, shall not be deemed to be &#147;filed&#148; for purposes of Section&nbsp;18 of the Securities Exchange Act of 1934, as amended (the &#147;Exchange Act&#148;), 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.</font></p>
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:4.0pt;">&nbsp;</font></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="1" face="Times New Roman" style="font-size:8.5pt;font-weight:bold;">Section&nbsp;9 &#151; Financial Statements and Exhibits</font></b></p>
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;"><b><font size="1" face="Times New Roman" style="font-size:8.5pt;font-weight:bold;">Item&nbsp;9.01 Financial Statements and Exhibits.</font></b></p>
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:3.0pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">(d)&nbsp;The following exhibits are furnished with this Current Report on Form&nbsp;8-K.</font></p>
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>
<table border="0" cellspacing="0" cellpadding="0" width="100%" style="border-collapse:collapse;width:100.0%;">
<tr>
<td width="9%" valign="top" style="border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 0in 0in;width:9.38%;">
<p style="margin:0in 0in .0001pt;"><b><font size="1" face="Times New Roman" style="font-size:7.0pt;font-weight:bold;">Exhibit&nbsp;No.</font></b></p>    </td>
<td width="4%" valign="bottom" style="padding:0in 0in 0in 0in;width:4.02%;">
<p style="margin:0in 0in .0001pt;"><b><font size="1" face="Times New Roman" style="font-size:1.0pt;font-weight:bold;">&nbsp;</font></b></p>    </td>
<td width="86%" valign="top" style="border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 0in 0in;width:86.6%;">
<p style="margin:0in 0in .0001pt;"><b><font size="1" face="Times New Roman" style="font-size:7.0pt;font-weight:bold;">Description</font></b></p>    </td>   </tr>
<tr>
<td width="9%" valign="top" style="border:none;padding:0in 0in 0in 0in;width:9.38%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>    </td>
<td width="4%" valign="bottom" style="padding:0in 0in 0in 0in;width:4.02%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>    </td>
<td width="86%" valign="top" style="border:none;padding:0in 0in 0in 0in;width:86.6%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>    </td>   </tr>
<tr>
<td width="9%" valign="top" style="padding:0in 0in 0in 0in;width:9.38%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">99.1</font></p>    </td>
<td width="4%" valign="bottom" style="padding:0in 0in 0in 0in;width:4.02%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>    </td>
<td width="86%" valign="top" style="padding:0in 0in 0in 0in;width:86.6%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">Press Release, dated July   25, 2013.</font></p>    </td>   </tr>
<tr>
<td width="9%" valign="top" style="padding:0in 0in 0in 0in;width:9.38%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>    </td>
<td width="4%" valign="bottom" style="padding:0in 0in 0in 0in;width:4.02%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>    </td>
<td width="86%" valign="top" style="padding:0in 0in 0in 0in;width:86.6%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>    </td>   </tr>
<tr>
<td width="9%" valign="top" style="padding:0in 0in 0in 0in;width:9.38%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">99.2</font></p>    </td>
<td width="4%" valign="bottom" style="padding:0in 0in 0in 0in;width:4.02%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>    </td>
<td width="86%" valign="top" style="padding:0in 0in 0in 0in;width:86.6%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">Quarter Ended June 30,   2013 Earnings Release and Supplemental Information, dated July 25, 2013.</font></p>    </td>   </tr>  </table>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">2<a name="PB_2_124132_7056"></a></font></p>
<div style="margin:0in 0in .0001pt;"><hr size="3" width="100%" noshade color="#010101" align="left"></div>
</div>
<!-- SEQ.=1,FOLIO='2',FILE='C:\JMS\pselva\13-17055-1\task6148723\17055-1-ba.htm',USER='105344',CD='Jul 24 22:18 2013' -->

<br clear="all" style="page-break-before:always;">
<div>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="1" face="Times New Roman" style="font-size:8.5pt;font-weight:bold;">SIGNATURES</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.</font></p>
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>
<table border="0" cellspacing="0" cellpadding="0" width="100%" style="border-collapse:collapse;width:100.0%;">
<tr>
<td width="24%" valign="top" style="padding:0in 0in 0in 0in;width:24.44%;">
<p style="margin:0in 0in .0001pt;"><b><font size="1" face="Times New Roman" style="font-size:1.0pt;font-weight:bold;">&nbsp;</font></b></p>    </td>
<td width="75%" colspan="4" valign="top" style="padding:0in 0in 0in 0in;width:75.56%;">
<p style="margin:0in 0in .0001pt;"><b><font size="1" face="Times New Roman" style="font-size:8.5pt;font-weight:bold;">CORESITE&nbsp;REALTY&nbsp;CORPORATION</font></b></p>    </td>   </tr>
<tr>
<td width="24%" valign="top" style="padding:0in 0in 0in 0in;width:24.44%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>    </td>
<td width="19%" valign="top" style="padding:0in 0in 0in 0in;width:19.06%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>    </td>
<td width="56%" colspan="3" valign="top" style="padding:0in 0in 0in 0in;width:56.5%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>    </td>   </tr>
<tr>
<td width="24%" valign="top" style="padding:0in 0in 0in 0in;width:24.44%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>    </td>
<td width="19%" valign="top" style="padding:0in 0in 0in 0in;width:19.06%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>    </td>
<td width="56%" colspan="3" valign="top" style="padding:0in 0in 0in 0in;width:56.5%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>    </td>   </tr>
<tr>
<td width="24%" valign="top" style="padding:0in 0in 0in 0in;width:24.44%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">Date: July 25, 2013</font></p>    </td>
<td width="19%" valign="top" style="padding:0in 0in 0in 0in;width:19.06%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">By:</font></p>    </td>
<td width="45%" colspan="2" valign="top" style="border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 0in 0in;width:45.0%;">
<p style="margin:0in 0in .0001pt;"><b><font size="1" face="Times New Roman" style="font-size:9.0pt;font-weight:bold;">/s/ Jeffrey S. Finnin</font></b></p>    </td>
<td width="11%" valign="top" style="padding:0in 0in 0in 0in;width:11.5%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>    </td>   </tr>
<tr>
<td width="24%" valign="top" style="padding:0in 0in 0in 0in;width:24.44%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:6.0pt;">&nbsp;</font></p>    </td>
<td width="19%" valign="top" style="padding:0in 0in 0in 0in;width:19.06%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:6.0pt;">&nbsp;</font></p>    </td>
<td width="19%" valign="top" style="padding:0in 0in 0in 0in;width:19.16%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:6.0pt;">&nbsp;</font></p>    </td>
<td width="37%" colspan="2" valign="top" style="padding:0in 0in 0in 0in;width:37.34%;">
<p style="margin:0in 0in .0001pt;"><b><font size="1" face="Times New Roman" style="font-size:6.0pt;font-weight:bold;">&nbsp;</font></b></p>    </td>   </tr>
<tr>
<td width="24%" valign="top" style="padding:0in 0in 0in 0in;width:24.44%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>    </td>
<td width="19%" valign="top" style="padding:0in 0in 0in 0in;width:19.06%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>    </td>
<td width="19%" valign="top" style="padding:0in 0in 0in 0in;width:19.16%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">Name:</font></p>    </td>
<td width="37%" colspan="2" valign="top" style="padding:0in 0in 0in 0in;width:37.34%;">
<p style="margin:0in 0in .0001pt;"><b><font size="1" face="Times New Roman" style="font-size:8.5pt;font-weight:bold;">Jeffrey   S. Finnin</font></b></p>    </td>   </tr>
<tr>
<td width="24%" valign="top" style="padding:0in 0in 0in 0in;width:24.44%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:6.0pt;">&nbsp;</font></p>    </td>
<td width="19%" valign="top" style="padding:0in 0in 0in 0in;width:19.06%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:6.0pt;">&nbsp;</font></p>    </td>
<td width="19%" valign="top" style="padding:0in 0in 0in 0in;width:19.16%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:6.0pt;">&nbsp;</font></p>    </td>
<td width="37%" colspan="2" valign="top" style="padding:0in 0in 0in 0in;width:37.34%;">
<p style="margin:0in 0in .0001pt;"><b><font size="1" face="Times New Roman" style="font-size:6.0pt;font-weight:bold;">&nbsp;</font></b></p>    </td>   </tr>
<tr>
<td width="24%" valign="top" style="padding:0in 0in 0in 0in;width:24.44%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>    </td>
<td width="19%" valign="top" style="padding:0in 0in 0in 0in;width:19.06%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>    </td>
<td width="19%" valign="top" style="padding:0in 0in 0in 0in;width:19.16%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">Title:</font></p>    </td>
<td width="37%" colspan="2" valign="top" style="padding:0in 0in 0in 0in;width:37.34%;">
<p style="margin:0in 0in .0001pt;"><b><font size="1" face="Times New Roman" style="font-size:8.5pt;font-weight:bold;">Chief   Financial Officer</font></b></p>    </td>   </tr>
<tr height="0">
<td width="183" style="border:none;"></td>
<td width="143" style="border:none;"></td>
<td width="143" style="border:none;"></td>
<td width="193" style="border:none;"></td>
<td width="86" style="border:none;"></td>   </tr> </table>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">3<a name="PB_3_125025_7056"></a></font></p>
<div style="margin:0in 0in .0001pt;"><hr size="3" width="100%" noshade color="#010101" align="left"></div>
</div>
<!-- SEQ.=1,FOLIO='3',FILE='C:\JMS\pselva\13-17055-1\task6148723\17055-1-ba.htm',USER='105344',CD='Jul 24 22:18 2013' -->

<br clear="all" style="page-break-before:always;">
<div>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="1" face="Times New Roman" style="font-size:8.5pt;font-weight:bold;">EXHIBIT&nbsp;INDEX</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>
<table border="0" cellspacing="0" cellpadding="0" width="100%" style="border-collapse:collapse;width:100.0%;">
<tr>
<td width="4%" valign="top" style="padding:0in 0in 0in 0in;width:4.58%;">
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="1" face="Times New Roman" style="font-size:7.0pt;font-weight:bold;">Exhibit</font></b></p>    </td>
<td width="5%" valign="top" style="padding:0in 0in 0in 0in;width:5.42%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>    </td>
<td width="90%" valign="top" style="padding:0in 0in 0in 0in;width:90.0%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>    </td>   </tr>
<tr>
<td width="4%" valign="top" style="border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 0in 0in;width:4.58%;">
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="1" face="Times New Roman" style="font-size:7.0pt;font-weight:bold;">No.</font></b></p>    </td>
<td width="5%" valign="top" style="padding:0in 0in 0in 0in;width:5.42%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>    </td>
<td width="90%" valign="top" style="padding:0in 0in 0in 0in;width:90.0%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>    </td>   </tr>
<tr>
<td width="4%" valign="top" style="border:none;padding:0in 0in 0in 0in;width:4.58%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>    </td>
<td width="5%" valign="top" style="padding:0in 0in 0in 0in;width:5.42%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>    </td>
<td width="90%" valign="top" style="padding:0in 0in 0in 0in;width:90.0%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>    </td>   </tr>
<tr>
<td width="4%" valign="top" style="padding:0in 0in 0in 0in;width:4.58%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">99.1</font></p>    </td>
<td width="5%" valign="top" style="padding:0in 0in 0in 0in;width:5.42%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>    </td>
<td width="90%" valign="top" style="padding:0in 0in 0in 0in;width:90.0%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">Press Release, dated July   25, 2013.</font></p>    </td>   </tr>
<tr>
<td width="4%" valign="top" style="padding:0in 0in 0in 0in;width:4.58%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>    </td>
<td width="5%" valign="top" style="padding:0in 0in 0in 0in;width:5.42%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>    </td>
<td width="90%" valign="top" style="padding:0in 0in 0in 0in;width:90.0%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>    </td>   </tr>
<tr>
<td width="4%" valign="top" style="padding:0in 0in 0in 0in;width:4.58%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">99.2</font></p>    </td>
<td width="5%" valign="top" style="padding:0in 0in 0in 0in;width:5.42%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>    </td>
<td width="90%" valign="top" style="padding:0in 0in 0in 0in;width:90.0%;">
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">Quarter Ended June 30,   2013 Earnings Release and Supplemental Information, dated July 25, 2013.</font></p>    </td>   </tr>  </table>
<p style="margin:0in 0in .0001pt;"><font size="1" face="Times New Roman" style="font-size:8.5pt;">&nbsp;</font></p>
<div style="margin:0in 0in .0001pt;"><hr size="3" width="100%" noshade color="#010101" align="left"></div>
</div>
<!-- SEQ.=1,FOLIO='',FILE='C:\JMS\pselva\13-17055-1\task6148723\17055-1-ba.htm',USER='105344',CD='Jul 24 22:18 2013' -->

</body>
</html>
[{"type": "8-K", "sequence": "1", "filename": "a13-17055_18k.htm", "description": "8-K", "secsgml_size_bytes": 37165}]
{"company-data": {"conformed-name": "CoreSite Realty Corp", "cik": "0001490892", "assigned-sic": "6798", "irs-number": "000000000", "state-of-incorporation": "MD", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "8-K", "act": "34", "file-number": "001-34877", "film-number": "13984966"}, "business-address": {"street1": "1050 17TH STREET", "street2": "SUITE 800", "city": "DENVER", "state": "CO", "zip": "80265", "phone": "(866) 777-2673"}, "mail-address": {"street1": "1050 17TH STREET", "street2": "SUITE 800", "city": "DENVER", "state": "CO", "zip": "80265"}}
UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 8-K
CURRENT REPORT
Pursuant to Section 13 OR 15(d) of The
Securities Exchange Act of 1934
Date of Report (Date of earliest event reported): July 25, 2013
CoreSite Realty Corporation
(Exact name of registrant as specified in its charter)
Maryland
001-34877
27-1925611
(State   or other jurisdiction
of incorporation)
(Commission
File Number)
(IRS   Employer
Identification No.)
1050 17th Street, Suite 800
Denver, CO
80265
(Address of principal executive   offices)
(Zip   Code)
Registrant's telephone number, including area code: (866) 777-2673
N/A
(Former name or former address, if changed since last report.)
Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:
o
Written   communications pursuant to Rule 425 under the Securities Act (17 CFR   230.425)
o
Soliciting   material pursuant to Rule 14a-12 under the Exchange Act (17 CFR   240.14a-12)
o
Pre-commencement   communications pursuant to Rule 14d-2(b) under the Exchange Act (17   CFR 240.14d-2(b))
o
Pre-commencement   communications pursuant to Rule 13e-4(c) under the Exchange Act (17   CFR 240.13e-4(c))
Section 2 — Financial Information
Item 2.02 Results of Operations and Financial Condition.
On July 25, 2013, CoreSite Realty Corporation ("CoreSite") issued a press release reporting financial results and operating information for the quarter ended June 30, 2013. 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.
Section 9 — Financial Statements and Exhibits
Item 9.01 Financial Statements and Exhibits.
(d) The following exhibits are furnished with this Current Report on Form 8-K.
Exhibit No.
Description
99.1
Press Release, dated July   25, 2013.
99.2
Quarter Ended June 30,   2013 Earnings Release and Supplemental Information, dated July 25, 2013.
2
SIGNATURES
Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.
CORESITE REALTY CORPORATION
Date: July 25, 2013
By:
/s/ Jeffrey S. Finnin
Name:
Jeffrey   S. Finnin
Title:
Chief   Financial Officer
3
EXHIBIT INDEX
Exhibit
No.
99.1
Press Release, dated July   25, 2013.
99.2
Quarter Ended June 30,   2013 Earnings Release and Supplemental Information, dated July 25, 2013.