Objective: This study used a sample cohort of Medicare-eligible patients to determine the yearly and regional variation in estimated annual costs (EAC) of all stand-alone Medicare Part D (MPD) plans. Methods: Fifty patients were randomly selected from a database of 18,000 Medicare-eligible patients provided by a pharmacy benefits management company. Each patient's medication history from January-June 2007 was used to generate their medication profile. Each profile was entered into the Medicare website and the EAC were calculated. For each patient the lowest, mean, and highest EAC were obtained for both 2007 and 2008 in each of the 34 MPD regions. EAC from 2007 were inflation-adjusted and compared to 2008 costs. Pair-wise comparisons were performed to analyze unadjusted and inflation-adjusted 2007 versus 2008 EAC differences within each region. Results: In some regions, significant increases were observed in the comparisons of 2007 EAC or inflation-adjusted 2007 EAC versus 2008 EAC. For example, in California all 2008 EAC values (lowest, mean, and highest) significantly increased from 2007 (both unadjusted and inflation-adjusted). This differed from other regions where there was no change or a decrease in EAC was observed. For example, in Alaska the lowest EAC were not statistically different between 2008 and 2007 (both unadjusted and inflation-adjusted). Mean EAC showed a significant decrease only when 2007 EAC were inflation adjusted, while highest 2007 EAC values (both unadjusted and inflation-adjusted) were significantly greater than the highest 2008 EAC. Conclusion: The privatization of MPD plans was intended to decrease drug acquisition costs and theoretically these savings would decrease drug costs for Medicare-eligible patients. However, based on the variable trends between MPD regions, and in some instances the increase in EAC from 2007 to 2008, drug costs incurred by patients do not appear to be decreasing between 2007 and 2008.