In westernized societies there is a consistent and continuous gradient between the prevalence of cardiovascular disease (including both coronary heart disease and stroke) with SES, such that people from lower SES have more disease. Several studies have examined the roles of the major cardiovascular risk factors for explaining this gradient. There is a strong SES gradient for smoking, which parallels the gradient in disease, but the gradients for hypertension and cholesterol are weak or absent. Central obesity and physical inactivity may also be contributory factors. In the United States there is a strong association between SES and race, and it is suggested that the higher prevalence of hypertension and cardiovascular disease in blacks may be attributed to psychosocial factors, including those related to SES. The possible pathways by which SES affects cardiovascular disease include effects of chronic stress mediated by the brain, differences in lifestyles and behavior patterns, and access to health care. At the present time, the second of these is the strongest candidate; the effects of stress have been little studied.