Crown Castle (CCI) 10-Q 2017 Q3 Quarterly report

Exhibit 32.1

Certification Pursuant to

18 U.S.C. Section 1350

As Adopted Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002

In connection with the Quarterly Report on Form 10-Q of Crown Castle International Corp., a Delaware Corporation (“Company”), for the period ending September 30, 2017 as filed with the Securities and Exchange Commission on the date hereof (“Report”), each of the undersigned officers of the Company hereby certifies pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that to the best of such officer's knowledge:

1) the Report complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

2) the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company as of September 30, 2017 (the last date of the period covered by the Report).

/s/ Jay A. Brown

Jay A. Brown

President and Chief Executive Officer

November 6, 2017

/s/ Daniel K. Schlanger

Daniel K. Schlanger

Senior Vice President and Chief Financial Officer

November 6, 2017

A signed original of this written statement required by Section 906 of the Sarbanes-Oxley Act of 2002 has been provided to Crown Castle International Corp. and will be retained by Crown Castle International Corp. and furnished to the Securities and Exchange Commission or its staff upon request.