We evaluated the possible additive effect of overweight and diabetes in the occurrence of coronary heart disease (CHD) and stroke, and their interaction with other established risk factors. In a cross-sectional study, we evaluated the frequency of CHD and stroke in four groups of subjects: (1) lean non-diabetic subjects (n=250); (2) lean diabetic subjects (n=269); (3) overweight non-diabetic subjects (n=203); and (4) overweight diabetic subjects (n=446). CHD was more frequent among diabetic subjects, and even more among overweight diabetic subjects; stroke was more frequent among diabetic subjects, but equally frequent in overweight and in lean diabetic subjects. At multiple logistic regression analysis, age, arterial hypertension, diabetes were independent risk factors for CHD and for stroke; BMI and hyperlipidemia were risk factors only for CHD. CHD was an independent risk factor for stroke, and stroke was a risk factor for CHD. We conclude that obesity and diabetes are additional risk factors for CHD but not for stroke. The value of established risk factors such as arterial hypertension and hyperlipidemia in determining the appearance of CHD and stroke is maintained in the presence overweight and diabetes. Finally, CHD is frequently associated with stroke, suggesting a common process of atherosclerosis underlying both diseases.