Diabetes mellitus is one of the most common chronic diseases affecting older persons in the United States. It occurs in 18% of persons between 65 and 75 years of age and in as many as 40% of persons over 80 years of age. The prevalence of diabetes mellitus varies considerably by ethnic group and is higher among most minority groups in the United States than among non-Hispanic white persons. Published data also show increased complications and mortality rate from diabetes in the minority groups. In this article, we review the current literature on the prevalence, complications, and mortality-rate effects of diabetes mellitus and the results of interventions in three major minority groups in the United States, namely African Americans, Hispanic Americans, and Native Americans. Recent studies of diabetes mellitus in Mexican seniors also are described. Our review focuses primarily on patients with non-insulin-dependent diabetes mellitus, because by far this is the most prevalent type in older persons.