OBJECTIVES: In 2008, there were currently 6 statins available in the U.S. market and more than 193 million statin prescriptions were written. We sought to examine the patterns of statin use among privately insured commercial and Medicare patients in the U.S. METHODS: A retrospective analysis was performed using MarketScan Commercial and Medicare data from Jan. 2008 to Dec. 2008. Two cohorts were created: 1) the commercial cohort (CC) and 2) the Medicare cohort (MC). Statin scripts of minimum 30 day supply were extracted from the pharmacy claims data and individual demographic and clinical information were linked from their medical and administrative records. Prescription patterns were examined and analyses by age and gender were performed. RESULTS: There were 18 million and 9.8 million statin prescriptions filled by the CC and MC, respectively. In both cohorts, simvastatin accounted for the largest share of statin prescriptions (MC: 44.1%; CC: 44.0%), followed by atorvastatin (MC: 31.6%; CC: 31.1%), rosuvastatin (MC: 7.8%; CC: 11.2%), pravastatin (MC: 8.1%; CC: 6.5%), lovastatin (MC: 7.4%; CC: 6.6%) and fluvastatin (MC: 0.9%; CC: 0.6%). The majority of statin prescriptions were for generics (MC: 59.6%; CC: 57.1%).The average annual number of statin prescription per user was 9.3 for the MC and 7.6 for the CC. In the CC, 58.1% of prescriptions were filled by male, while 50.4% of prescriptions were filled by male in the MC. Diabetic patients accounted for 35.2% of prescriptions in the MC, and 26.8% in the CC. Milligram dosing distributions (mean; median; mode) were for simvastatin (MC:32.1; 20;20 CC:32.9;20;40); atorvastatin (MC:24.3;20;10 CC:24.7;20;10); rosuvastatin (MC: 12.7;10;10 CC:13.1;10;10); and pravastatin (MC:37.6;40;40 CC:38.2;40;40). CONCLUSIONS: This analysis suggests different statin use patterns by age, gender, and insurance. Most frequently dispensed doses were 20 mg for simvastatin, 10 mg for atorvastatin and rosuvastatin, and 40 mg for pravastatin.