OBJECTIVES: The purpose of this study was to determine the prevalence of diabetes mellitus in Hawaii from insurance claims data. METHODS: Information from two major health plans covering approximately 66% of the state's population was used to estimate prevalence rates by sex, age group, and geographic area. Weighted multiple linear regression was applied to identify predictors of diabetes prevalence. RESULTS: The statewide diabetes prevalence was estimated at 43.8 per 1000 persons. The ethnic composition of the population and rural residence partially explained the geographic variation in diabetes prevalence. CONCLUSIONS: Insurance claims data may be a useful tool for population-based diabetes surveillance.