In this systematic evidence review (SER), we evaluate data on the relationship between the use of postmenopausal hormone replacement therapy (HRT) and selective estrogen receptor modulators (SERMs) and the risk for venous thromboembolism. We present results of a review of the literature and a meta-analysis of studies reporting data on postmenopausal HRT and venous thromboembolism. This report is part of a larger project on the risks and benefits of HRT prepared for the U.S. Preventive Services Task Force (USPSTF) to assist them in making recommendations. The emerging emphasis on women's health, coupled with an aging population, makes it increasingly important for primary care physicians to be familiar with the risks and benefits of postmenopausal HRT. Although postmenopausal HRT is widely used, it poses important health risks. One suspected risk is an increase in venous thromboembolic events. Initially, this relationship was based on studies of oral contraceptives and was not supported by studies of HRT. Findings from more recent studies, however, indicate an increase in risk.