The epidemiology of impaired glucose tolerance and hypertension. Epidemiologic research indicates that glucose intolerance and hypertension are interrelated phenomena, each powerfully predisposing to atherosclerotic cardiovascular disease. Both diabetic and hypertensive patients have greater amounts of atherogenic risk factors, including dyslipidemia, hyperuricemia, elevated fibrinogen, and left ventricular hypertrophy. Diabetic persons have an increased prevalence of hypertension (50%), and glucose intolerance is more common in hypertension (15% to 18%). Both share a strong relationship to excess weight, but the excess of hypertension in diabetic persons occurs in both lean and obese subjects. Diabetes doubles the risk of hypertension associated with overweight. The risk of coronary disease, stroke, and peripheral arterial disease increases with increasing blood pressure to the same degree in diabetic persons as in nondiabetic persons, but at any level of blood pressure, diabetic persons have a doubled risk of these outcomes. Both diabetic and hypertensive patients are particularly prone to silent or unrecognized myocardial infarctions. Greater efforts at primary prevention of both hypertension and diabetes are clearly needed, including efforts at weight control, exercise, limitation of salt intake, and control of blood lipid levels. In either diabetic or hypertensive candidates for cardiovascular disease, optimization of the chances of avoiding sequelae requires a comprehensive multifactorial approach. Prevention requires more than normalization of either the blood sugar or blood pressure. Rational preventive measures must also include weight reduction, a fat-modified diet, cessation of smoking cigarettes, raising high-density lipoprotein, lowering low-density lipoprotein, and reduction of fibrinogen. Hypertension, obesity, insulin resistance, hyperinsulinemia, hypertriglyceridemia, and low high-density lipoprotein cholesterol tend to coexist. 