A large quantity of epidemiological data has accumulated attesting to a link between social support and the progression of cardiovascular disease in cardiac patients. One way that social support might exerts its health effects is by attenuating physiological responses to psychological stress, since these responses have been related to cardiovascular disease. Much myocardial ischemia occurring during daily life appears to be related to periods of psychological stress, and laboratory mental stress tasks have been found to induce ischemia. Thus, the incidence, severity, and duration of myocardial ischemia might be modified by changes in the social environment.