Cardiovascular disease is the leading cause of death among postmenopausal women. Growing evidence exists that hormone replacement therapy (HRT) may reduce cardiovascular disease and mortality. This has led to the use of postmenopausal HRT for primary prevention of heart disease, however it remains unresolved which women are likely to benefit most from this clinical approach. This is a complicated question because many potential mechanisms are involved by which hormone therapy (HRT) may confer cardioprotection. The Postmenopausal Estrogen/Progestins Intervention (PEPI) trial examined the relative impact of four regimens of hormone therapy on a range of cardiovascular disease risk factors (e.g. lipids, blood pressure, insulin/glucose, hemostasis factors). The trial was well conducted; its data have been thoroughly edited and have yielded a series of important publications. To date, however, publications have focused on average effects without a thorough exploration of the range of, and interplay among, the various effects across the 875 enrolled in the trial.