A rise in coronary heart disease incidence after menopause and a dramatic increase in the severity of the presenting diseases are noted in a cohort of 2873 Framingham women who were followed up for 24 years. No premenopausal woman developed a myocardial infarction or died of coronary heart disease. Such events were common in postmenopausal women. Even in women under 55, 40% of the postmenopausal coronary heart disease presented in these more serious forms, whether menopause was natural or surgical. The contrast was especially marked in the age group 40 to 44 years. In the age groups 45 to 49 and 50 to 54 years, incidence rates in menopausal and postmenopausal intervals were more than double those in premenopausal intervals, whether menopause was natural or surgical. In surgical menopause there was excess incidence whether the ovaries were removed or not. Postmenopausal women on hormones had a doubled risk of coronary heart disease.