OBJECTIVES: To identify the determinants of drug adherence among statin users in a Medicaid managed care population. METHODS: Retrospective database analysis of Maryland Medicaid medical and pharmacy claims for the period January 1, 2001 - December 31, 2003. Inclusion criteria: Continuously enrolled patients older than 18 years who had at least one prescription claim for any of the statins. Exclusion criteria (to obtain incident cohort): Patients who had at least a claim before July 1st, 2002. Non-adherence was defined as a failure to refill a prescription claim. Logistic regression models were built to determine the association of age, gender, race, and comorbidities (based on Charlson Comorbidity Index) with drug adherence.RESULTS: Out of a total 1,997 patients, 61% females, 57% African Americans, and 70% 60 years old or younger. Caucasians were more adherent than African Americans (30% vs. 22%), younger patients less adherent than older patients (24% vs. 26%) and females less adherent than males (22% vs. 28%). In the logistic multivariate model, adjusting for demographics and comorbidities, African Americans (OR 0.68, 95% CI 0.549, 0.841), and males (OR 1.33, 95% CI 1.083, 1.641) were significantly more likely to adhere to statin therapy. CONCLUSION: In this Medicaid population, adherence to statin pharmacotherapy is lower among females and African Americans. The effectiveness of adherence programs may be improved if they are earmarked to these specific subpopulations.