Coronary heart disease is the leading cause of death in adult women in the U.S. Since clinical manifestations of coronary disease predominate in postmenopausal women, the need to evaluate coronary disease-gonadal hormone relationships is compelling. Further, estrogen exerts biologically plausible benefits: improved lipid profile, lower fibrinogen levels, favorable changes in vascular reactivity, possible antioxidant effects, among others. Although observational studies of estrogen use suggest substantial lessening of coronary risk, selection biases favoring a healthy cohort of women mandate randomized clinical trial data, with such trials currently in progress. Information is lacking regarding benefit: risk ratios of transdermal estrogen and estrogen/progestin combinations as coronary preventive therapies.