A recently presented hypothesis contends that the excess coronary heart disease mor-tality associated with hypertension is more prominent in lean men than in overweight men. This hypothesis was addressed using data collected in the Israeli Ischemic Heart Disease Study (n = 10,059). The ratios of age-adjusted 15-year death rates in hypertensive and normotensive men were 4.7,2.8,2.0, and 1.9 in the Quetelet index groups of <2.29,2.29 to 2.56,2.56 to 2.83 and >2.83 g/cm 2, respectively. The corresponding ratios for all-cause mortality were 2.2,2.1,2.0, and 1.7, respectively. The group with the highest all-cause age-adjusted mortality, at 33.6%, was that of the leanest (<2.29 g/cm, bottom 20% of the Quetelet index distribution) hypertensive subjects. The same group also displayed the highest coronary heart disease mortality (age-adjusted rate, 18.2%). The findings persisted for both smokers and nonsmokers and after exclusion of men with coronary heart disease or diabetics at intake, men on antihypertensive medication, or those who died in the first 2 years of follow-up (1963–1965). A multivariate risk score for developing myocardial infarction was calculated, based on levels of age, systolic blood pressure, total cholesterol, high density lipoprotein cholesterol, cigarette smoking, diabetes mellitus, and Quetelet index. This score varied little across the four Quetelet index groups in hypertensive men: 5-year mean estimated risks of myocardial infarction were between 70 and 74/1000. In normotensive men the scores increased from 19/1000 in the leanest subjects to 29/1000 in the overweight ones. The overall trend of 15-year coronary heart disease mortality is thus in line with the multiple risk of 5-year myocardial infarction incidence, but the source of the risk differences between lean and overweight hypertensive subjects remains unclear. These findings may have important implications in making decisions regarding the mode of treatment, especially in the wide group of mildly hypertensive persons in whom the benefit of treatment is still controversial. The treating physician who wishes to make a therapeutic decision might need to consider low body weight as either inherently representing or associated with an unfavorable progno-sis.