The prevalence of hyperglycemia in two American Indian tribes, the Washoe and Northern Paiute, was evaluated by determining the number of individuals aged fifteen years and older with a history of concurrently treated diabetes or with a plasma glucose level of at least 160 mg./100 ml. (Auto Analyzer) two hours after a 75-gm. glucose equivalent load. One hundred and twelve Washoe Indians, representing 74.2 per cent of the Washoe study population, and 131 Paiute Indians, 60.6 per cent of the Paiute study population, were examined. The prevalence of hyperglycemia was 10.7 per cent for the Washoe and 11.5 per cent for the Paiute group. These rates, when adjusted for age and sex, did not differ significantly from each other or from that reported for the Cocopah Indians. The adjusted rates for these three tribes were significantly lower than the adjusted rate for the Pima. In both the Washoe and Paiute populations, the prevalence of hyperglycemia increased with age, but was not related to parity.