THE CORPORATE LIBRARY

Related Party Transactions and Outside Related Director Information

Westlake Chemical Corporation (WLK)

4/3/2006 Proxy Information

Ms. Jenkins is the sister of James Chao and Albert Chao.

Mr. Chao, along with his brother Albert Chao, assisted their father T.T. Chao in founding Westlake and served as Westlake’s first president from 1985 to 1996.

The office space for our principal executive offices in Houston, Texas is leased, at market rates, from an affiliate, Westlake Post Oak Center, Ltd., under a lease that expires on February 28, 2010. Total annual payments under the lease in 2005 were approximately $1.2 million.

Effective July 1, 2004, Westlake Management Services, Inc. (WMS) and Titan Petrochemical & Polymers Berhad (now known as Titan Chemicals Corp. Bhd), a Malaysian affiliate of our principal stockholder, entered into a service level agreement under which WMS provides services to Titan Chemicals Corp. Bhd. The basic fee under the agreement is $0.5 million per year, plus additional reimbursements of actual costs, overhead, administrative fees, and/or profit margin for certain additional services. The agreement expires on June 30, 2007. WMS received $0.5 million for services under the agreement in 2005.

Effective as of July 1, 2004, WMS entered into a technical assistance agreement with WEC International Corporation, or WECI, a former affiliate of ours, on behalf of Suzhou Huasu Plastics Co. Ltd., a joint venture in which we have a 43% interest, whereby WMS will perform certain technical and administrative services, including technical training, engineering, plant operations and project management for WECI and/or Suzhou Huasu Plastics. WMS will charge WECI $49,000 per year, plus reimbursement for all direct costs, including costs associated with providing expatriates to Suzhou Huasu Plastics, plus an overhead charge and profit margin. WMS received $49,000 for these services in 2005.

In addition, effective as of January 1, 2004, our subsidiary WMS entered into an agreement with our affiliate Gulf United Investments Corporation, or GUIC, to perform certain administrative services, including tax, accounting, human resources, legal and risk management, for GUIC on behalf of itself and on behalf of TTWF LP, our principal stockholder, and its affiliates Westlake Industries, Inc., or WII, and Tanglewood Property Management Co., or TPMC, for an annual base fee of $300,000, based upon actual costs, a pre-determined percentage of overhead and profit margin. In addition to this base fee, GUIC will reimburse WMS for all direct costs and expenses incurred by WMS on behalf of GUIC and those affiliates in the course of providing services under the agreement. GUIC will also reimburse WMS for a pre-determined percentage of overhead and profit margin of WMS for certain services. This agreement was subsequently modified in 2004 to have TTWF LP replace GUIC as the signatory to the agreement. This modification did not change any other terms and conditions of the agreement, and WMS still performs the above-described services for GUIC, TTWF LP, WII and TPMC. WMS received $300,000 for these services in 2005.