Two hypotheses have been proposed to account for the effects of social support on cardiovascular morbidity and mortality. Both hypotheses operate through effects on risk factors for coronary heart disease, specifically arterial blood pressure and serum lipids. The stress- buffering hypothesis states that social support functions as a social resource for individuals exposed to social stressors; those persons with more support are less vulnerable to the risk-enhancing effects of stressors. The health behavior hypothesis states that persons with more support engage in more positive health behaviors, such as avoiding tobacco; moderate alcohol use; exercise; and, a prudent diet. A major limitation in research to evaluate these alternative hypotheses has been the failure to conceptualize and measure social support in a way appropriate to detect its effects in varying social and cultural contexts. This is a major issue in research in sub-cultural communities that are also high risk communities, such as African-Americans.