EXHIBIT 21

SUBSIDIARIES OF WESTLAKE *

Name of Subsidiary		State or Other Jurisdiction of Incorporation or Organization		Names Doing Business
North American Pipe Corporation		Delaware		North American Pipe Corporation and NAPCO
Westech Building Products, Inc.		Delaware		Westech Building Products, Inc.
Westech Building Products ULC		Canada		Westech Building Products ULC and Westech Building Products Limited
Westlake Ethylene Pipeline Corporation		Delaware		Westlake Ethylene Pipeline Corporation
Westlake Longview Corporation		Delaware		Westlake Longview Corporation
Westlake Management Services, Inc.		Delaware		Westlake Management Services, Inc.
Westlake Petrochemicals LLC		Delaware		Westlake Petrochemicals LLC, Westlake Petrochemicals LP and WPE
Westlake Polymers LLC		Delaware		Westlake Polymers LLC, Westlake Polymers LP and WPE
Westlake PVC Corporation		Delaware		Westlake PVC Corporation
Westlake Styrene LLC		Delaware		Westlake Styrene LLC and Westlake Styrene LP
Westlake Supply and Trading Company		Delaware		Westlake Supply and Trading Company
Westlake Vinyls Company LP		Delaware		Westlake Vinyls Company LP
Westlake Vinyls, Inc.		Delaware		Westlake Vinyls, Inc., Westlake Monomers and WCAO
WPT LLC		Delaware		WPT LLC and WPT LP
Suzhou Huasu Plastics Co., Ltd. **		People’s Republic of China		Suzhou Huasu Plastics Co., Ltd. and Huasu

* Westlake has elected to omit the names of certain subsidiaries. None of the omitted subsidiaries, considered either alone or together with the other omitted subsidiaries of its immediate parent, constitutes a “Significant Subsidiary” as set forth in Section 601(b)(21) of Regulation S-K.

** Westlake owns 59% of this entity but accounts for it using the equity method.