OBJECTIVES: To determine the impact of adherence to statin therapy on the incidence of cardiovascular events 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 drug adherence adjusted for age, gender, race, comorbidities (based on Charlson Comorbidity Index) with cardiovascular events. RESULTS: Out of a total of 1997 patients, most were females (61%), African Americans (57%), and 60 years old or younger (70%). Based on univariate analysis, persistent patients had a lower incidence of cardiovascular events than non-persistent patients (19% vs. 32%), females a lower incidence than males (24% vs. 35%) and African Americans a lower incidence than Caucasians (24% vs. 34%). In the logistic regression model adjusting for comorbidities and demographics, drug adherence (OR 0.460, 59% CI 0.357, 0.593 ), African American race (OR 0.596, 95%CI .485, 0.734), and male gender (OR 1.674, 95% CI 1.369, 2.047) were significantly associated with CV events. CONCLUSION: In this Medicaid population of statin users, the incidence of cardiovascular events is higher in males, Caucasians and in patients who do not adhere to statin therapy. Risk management programs may need to focus on drug adherence among statin users, as one of the major modifiable factors to reduce cardiovascular events.