A large number of studies of disparate design are reasonably consistent in demonstrating that women with early bilateral oophorectomy are at increased risk of coronary heart disease. The evidence for an increase in risk among women with a surgical menopause but without bilateral oophorectomy is inconclusive, but such an effect, if any, could plausibly be explained by decreased ovarian function in many of those women as a consequence of the surgery. These findings, taken together with the lack of excess risk in women with bilateral oophorectomy who take replacement estrogen, support the view that the increased risk is due to estrogen deficiency. This view is further supported by the improvement in the lipid profile induced by estrogen replacement therapy in postmenopausal women. Because ovarian function begins to decline well before menopause, and continues to decline after menopause, it is not surprising that the moment of menopause is not associated with an abrupt increase in risk of heart disease. Moreover, some time is required for the adverse changes in coronary risk factors that occur during the climacteric to be reflected in increased rates of coronary disease. Although natural menopause does not cause an immediate increase in risk of heart disease, it does signal a period of increasing risk that is probably related both to age and to estrogen deficiency.