The Strong Heart Study, a study of cardiovascular disease among American Indians, was conducted to determine cardiovascular disease rates and the prevalence of risk factors among members of 13 tribal groups in South Dakota/North Dakota (SD/ND), southeastern Oklahoma, and Arizona. From 1989 to 1992, 4,549 tribal members aged 45-74 years (62% of eligible participants) were surveyed and examined for cardiovascular disease and its risk factors. Mean total cholesterol concentrations were over 20 mg/dl lower among the men and 27 mg/dl lower among the women than national mean levels for the same age groups. Cholesterol levels varied by tribal group; Arizona Indians had mean levels more than 20 mg/dl lower than those of SD/ND Indians. The prevalence of hypercholesterolemia was almost twice as high among SD/ND Indians as among Arizona Indians, but the rates for all three groups were much lower than total US rates (all races). Mean levels of high density lipoprotein cholesterol were lower among Indian men and women than in the US population as a whole. The prevalence of hypertension among Arizona and Oklahoma Indians was higher than that for the entire United States. SD/ND Indians had significantly lower mean blood pressures and prevalence rates of hypertension than Oklahoma and Arizona Indians and the United States as a whole. The prevalence of cigarette smoking was higher for all Indian groups except Arizona women in comparison with US rates. Smoking rates were highest in SD/ND and lowest in Arizona. Indian smokers smoked fewer cigarettes per day than the average US smoker. Arizona Indians had the highest prevalence of diabetes mellitus; over 60% of those participants were diabetic. In Oklahoma and SD/ND, one third of the men and over 40% of the women were diabetic. In addition, 13-20% of the participants had impaired glucose tolerance. Proteinuria was also a common problem; almost half of the Arizona Indians had micro- or macroalbuminuria, and 20% of Oklahoma and SD/ND Indians had significant proteinuria. The prevalence of obesity was high in all three groups, with Arizona Indians having the highest rates and the highest mean body mass indices. The prevalence of current alcohol use was lower among Indians than in the nation as a whole, but binge drinking was common among those who used alcohol. These results indicate that cardiovascular disease risk factors vary significantly among tribal groups. Prevention programs tailored toward decreasing the prevalence of risk factors are recommended for long-term reduction of cardiovascular disease rates in American Indian communities.