Objective: Upon implementation of Medicare Part D in 2006, Medicaid and Medicare dual-eligibles were shifted to Part D for their prescription drug coverage. This shift affected the utilization and market share of medications under Medicaid. This study focuses on statins which are widely prescribed. The objectives were: 1) to describe the number of units dispensed, the number of prescriptions, and total expenditures for statins in 2005 and 2006, nationally and for each state, and 2) to assess the shift in market share for these drugs between 2005 and 2006. Methods: Summary claims data for 11 commonly prescribed statins were obtained from the Centers for Medicare and Medicaid Services website for all US states for 2005 and 2006. Total units of statins reimbursed, total number of prescriptions, total reimbursement amount, and percent market share were calculated for each of the statins and for each of the 50 states. Results: The total units of statins reimbursed decreased from 573.5 million in 2005 to 201.0 million in 2006, as did the total number of prescriptions (17.5 million in 2005 vs. 6.2 million in 2006), and the total reimbursement amount ($1.8 billion in 2005 vs. $0.66 billion in 2006). The percentage market share of Lipitor® units decreased from 48.7% in 2005 to 42.8% in 2006. Similar trends were observed for percentages of prescriptions and reimbursement amounts. Zocor® also showed the same trend while Vytorin® and generic statin use increased. State wise comparisons show variability among states with CA and NY having the highest statin use. Conclusion: Overall, the findings of the study indicate a substantial decrease in statin prescriptions covered by Medicaid for the year 2006. This decrease in utilization along with the shift to generic statins affects the rebates received by Medicaid.