The relation of dietary factors and physical activity to hyperinsulinemia was examined in 389 men aged 70–89 years who participated in the Zutphen Elderly Study in 1990. Information about the usual diet was obtained using a cross-check dietary history, and habitual physical activity was assessed using a validated questionnaire. Known and newly diagnosed diabetic patients were excluded from this study, since serum insulin and C-peptide levels are indicators of insulin resistance and hyperinsulinemia in nondiabetics only. Insulin levels during the oral glucose tolerance test were lowest in men with the highest physical activity. This inverse association was independent of age, body mass index, the ratio of subscapular to triceps skinfold thickness, cigarette smoking, and energy intake (p > 0.001). In addition, insulin levels were inversely associated with the intake of dietary fiber and polyunsaturated fatty acids, which could not be accounted for by variables such as energy intake, body mass index, physical activity, prescribed diets, or the presence of coronary heart disease. In contrast, insulin levels increased with the increasing intake of saturated fatty acids and alcohol. The fasting C-peptide level was independently associated with the intake of total fat, saturated and monounsaturated fatty acids, and alcohol, whereas an inverse relation with the intake of total carbohy drates and dietary fiber was seen. Besides overweight, physical activity and dietary factors such as the intake of fatty acids, fiber, carbohydrates, and alcohol, were inde pendently associated with hyperinsulinemia and insulin resistance. Therefore, these behavioral factors may partly determine the occurrence of non-insulin-dependent diabetes mellitus and coronary heart disease and play a role in the prevention of these disorders.