Exhibit 21

MasTec, Inc.

AFFILIATED ENTITIES

December 31, 2014

NORTH AMERICA

Big Country Energy Services, Inc. (Canada)	(100% by Fabcor Targetco Ltd. (Canada)) (100% by 1867064 Alberta ULC (Canada)) (100% owned by MasTec Cooperateif (UA))
Big Country Energy Services LLC.(US) (CO)	(100% owned by MasTec North America, Inc.)
Bottom Line Services, LLC (DE)	(94% owned by MasTec North America, Inc.) (6% owned by Alan Roberts)
Dynamic Tower Services, Inc. (LA)	(100% owned by MasTec North America, Inc.)
EC Source Services, LLC (FL)	(100% owned by MasTec, Inc.)
MasTec Network Solutions, LLC f/k/a Nsoro MasTec, LLC (FL)	(100% owned by MasTec, Inc.)
MasTec North America, Inc. (FL)	(100% owned by MasTec, Inc.)
Pacer Construction Holdings Corporation (PCHC) (Canada)	(100% owned by 1828200 Alberta Ltd. (Canada)) (100% owned by 1867064 Alberta ULC (Canada)) (100% owned by MasTec Cooperateif (UA))
Pacer Foundations Corporation (PFC)	(100% owned by PCHC)
Pacer Foundations Construction Corporation	(100% owned by PFC)
Pacer Construction Corporation	(100% owned by PCHC)
Pacer Construction Management Corporation	(100% owned by PCHC)
Pacer Projects Corporation	(100% owned by PCHC)
Pacer Mamisiwin Corporation (PMC)	(100% owned by PCHC)
Pacer Mamisiwin Construction Corporation	(100% owned by PMC)
Pacer Newfoundland and Labrador Corporation	(100% owned by PCHC)
Patch Point Energy Services LTD. (Canada)	(100% owned by BC Acquisition II, LTD. (Canada)) (100% owned by 1867064 Alberta ULC (Canada)) (100% owned by MasTec Cooperateif (UA)
Precision Acquisition, LLC (WI)	(100% owned by MasTec, Inc.)
Precision Pipeline LLC (WI)	(100% owned by Precision Acquisition, LLC)
Pumpco, Inc. (TX)	(100% owned by MasTec North America, Inc.)
Wanzek Construction, Inc. (ND)	(100% owned by MasTec North America, Inc.)
WesTower Communications, Inc. (DE)	(100% owned by MasTec Network Solutions, LLC (FL))

Certain other affiliates have been omitted because, in the aggregate, they would not constitute a significant subsidiary.