OBJECTIVE - To examine racial variation in the poor control of GHb, a GHb value >9.5%, or GHb not tested in 1999 among Medicare beneficiaries aged 65-75 years enrolled in managed care plans. RESEARCH DESIGN AND METHODS - The National Committee on Quality Assurance provides person-level data regarding diabetes care services and control for Medicare beneficiaries enrolled in managed care to the Centers for Medicare and Medicaid Services (CMS). We merged this information with information on each individual's race, as well as other person-level and plan-level characteristics obtained from CMS. Bivarate and multivariate analyses were performed. RESULTS - The overall rate of poor GHb control was 32.7%. The age- and sex-adjusted rate of poor control among whites was 32.0%. This rate was significantly higher than the rate among Asians (24.7%) but significantly lower than the rate among blacks (40.6%) and Hispanics (36.5%) (P < 0.001). An increase in the number of comprehensive diabetes care measures received by an individual was associated with a significantly lower percentage of individuals with poor GHb control in all race groups. After controlling for the individual-level, plan-level, and diabetes care measure variables, the difference in GHb control between Asians and whites disappeared. However, blacks and Hispanics continued to have significantly higher rates of poor control than whites. CONCLUSIONS - There is room for significant reduction in the number of patients with poor control of GHb among all races, particularly among blacks and Hispanics.