Obesity is an important risk factor for cardiovascular diseases and non-insulin-dependent diabetes, which are chronic diseases that afflict American Indians and Alaska Natives today. Because American Indians are not represented in most national health and nutrition surveys, there is a paucity of data on actual prevalence of obesity in American Indians. We estimated prevalence of overweight and obesity for American Indian adults, school-age children, and preschool children from existing data. The prevalence of obesity in adults was estimated from self-reported weights and heights obtained from a special survey of American Indians performed as part of the 1987 National Medical Expenditure Survey. Prevalence of obesity in American Indians was 13.7% for men and 16.5% for women, which was higher than the US rates of 9.1% and 8.2%, respectively. Obesity rates in American Indian adolescents and preschool children were higher than the respective rates for US all-races combined.