PURPOSE: To examine community differences in cardiovascular disease (CVD) risk factors among black and white young adults by combining data from two large epidemiologic studies. METHODS: Data are from participants aged 20- 31 years in the Coronary Artery Risk Development In Young Adults (CARDIA) study (1987-1988; N = 4129) and the Bogalusa Heart study (1988-1991; N = 1884), adjusting for data collection differences prior to analysis. CARDIA includes four urban sites: Birmingham, Alabama; Chicago, Illinois; Minneapolis, Minnesota; and Oakland, California. Bogalusa is a semi-rural town in Southeastern Louisiana. CVD risk factors examined were smoking status, body habitus, and blood pressure. RESULTS: In Birmingham and Bogalusa, more white than black women were current smokers; no ethnic differences were observed among men. In Chicago, Minneapolis, and Oakland, more blacks were current smokers than were whites. For all sites, educational level was strongly inversely related to current smoking status; ethnic differences were more apparent among those with up to a high school education. Among white men and women, prevalence of obesity (body mass index > 31.1 kg/m2 in men and 32.3 kg/m2 in women) was greater in Birmingham and Bogalusa than in Chicago, Minneapolis, and Oakland. Mean systolic blood pressures were highest in Bogalusa, and the proportion of black men with elevated blood pressure (≤ 130/85 mmHg) was higher in Bogalusa and Birmingham. CONCLUSIONS: Community and ethnic differences in CVD risk factors were observed among young adults in two large epidemiologic studies. Further studies may enhance our understanding of the relationship of geographic differences in CVD risk to subsequent disease.