The prevalence of diagnosed diabetes among American Indians in New Mexico with varied genetic and cultural backgrounds is reported. Utilizing community-based registries, the prevalence in persons ages 35 years and older ranged from 9.8 percent among Jicarilla Apache Indians to 28.2 percent among Zuni Indians. All rates were significantly higher than the U.S. rate of 5.3 percent for the same age group. In addition, in three of the five tribal groups examined, the rates of diagnosed diabetes in Indians less than 35 years of age (range from 0.5 percent to 1.3 percent) were significantly higher than the U.S. rate of 0.4 percent for the same age group. The prevalence rates of diagnosed diabetes found in this study of American Indians in New Mexico were intermediate between those for the United States as a whole and the Pima Indians of southern Arizona. Reasons for the variations and the relative contribution of obesity, fitness, or genetic risk in the development of diabetes need further study.