Data from the Framingham Study and other population studies indicate that intermittent claudication (IC) sharply increases in late middle age and is somewhat higher among men than women. Noninvasive testing in populations indicates that the true prevalence of peripheral arterial disease (PAD) is at least five times higher than would be expected based on the reported prevalence of IC. Peripheral arterial disease correlates most strongly with cigarette smoking and either diabetes or impaired glucose tolerance. Other risk factors for PAD include hypertension; low levels of high-density lipoprotein cholesterol; and high levels of triglycerides, apolipoprotein B, lipoprotein(a), homocysteine, fibrinogen and blood viscosity. Individuals with PAD are more likely to have coronary heart disease and cerebrovascular disease than those without PAD. Because of the high risk of both nonfatal and fatal cardiovascular disease (CVD) events in PAD patients, individuals with evidence of PAD should undergo both a careful examination of the entire cardiovascular system and aggressive modification of CVD risk factors.