Little is known about the relation of overweight to risk of coronary heart disease in older women. In this paper, the authors used measured weight for 1,259 white women aged 65-74 years from the Epidemiologic Follow-up Study of the First National Health and Nutrition Examination Survey to examine the effect of overweight on coronary heart disease incidence (mean length of follow-up, 14 years). They also used reported lifetime maximum weight to examine the effect of weight loss on this association. Women with a Quetelet index (weight (kg)/height (m)2) of 29 or more showed an increased risk of coronary heart disease (relative risk (RR) = 1.5, 95% confidence interval (CI) 1.1-2.1) after adjustment for age and smoking in comparison with those with a Quetelet index of less than 21, while women with a Quetelet index of 23-24 had a lower risk of coronary heart disease (RR = 0.6, 95% CI 0.4-0.9). However, the pattern of risk associated with measured weight was modified by weight loss. Among heavier women whose weight was relatively stable, those with a Quetelet index of 29 or more had an increased risk of heart disease (RR = 2.7, 95% CI 1.7-4.4). Among those with greater weight loss, the relation between Quetelet index and risk of coronary heart disease was J-shaped. Overweight is an independent risk factor for coronary heart disease in older women, a finding strengthened after previous weight loss is accounted for. Reasons for the unexpected increase in risk of coronary heart disease in thinner women who lost weight are unclear, and further investigation is warranted.