The prevalence of diabetes mellitus in Alaska Natives has been thought to be low, but no survey of this condition in all natives has been conducted. Medical records from 1979 to 1985 were reviewed to determine the prevalence of diagnosed diabetes mellitus in Alaska Natives. Computerized outpatient and inpatient medical record data and clinician reports were used to identify cases. As of December 1985, 610 living Alaska Natives fulfilled diagnostic criteria for diabetes. Type II diabetes mellitus was found in 564 subjects, type I diabetes was found in 15 subjects, and unspecified type of diabetes was found in 31 subjects. The overall age-adjusted prevalence of diabetes mellitus, 15.7/1000, was lower than the overall United States rate of 24.7/1000. However, age-adjusted prevalence varied considerably by ethnic group; the prevalence was 27.2/1000 among Aleuts, 22.0/1000 among Alaskan Indians, and 8.8/1000 among Alaskan Eskimos. Rates within the Eskimo subgroups varied by a factor of four. Compared with previous reports, the prevalence of diabetes mellitus in Alaskan Eskimos appears to have increased. Diabetes mellitus is no longer a rare condition among Alaska Natives.