OBJECTIVES The Medicare Part D prescription drug benefit was introduced for Medicare enrollees to obtain prescription drug coverage. The 2006 benefit did not provide insurance coverage for standard prescription drug plan (PDP) members who incurred prescription costs between $2250 and $3600 dollars (referred to as the “doughnut hole”). We evaluated whether the “doughnut hole” was a factor in altering the prescription fulfillment decisions of Part D members. METHODS In the current retrospective cohort study, 750 pharmacy adjudication records from a national Part D HMO pharmacy database were investigated for the year 2006. Five hundred participants (standard PDP members) without coverage in the doughnut hole were compared to a group of 250 participants (enhanced PDP members) whose prescription coverage did not lapse in the doughnut hole. All participants were analyzed via a multivariate strategy for their prescription fulfillment decisions which were recorded as an endpoint of filling, delaying, switching, or stopping their respective medication. RESULTS From 72% of the standard PDP members who experienced the doughnut hole and altered their prescription decision, it was determined that 22% delayed medication, 13% switched medication, 10% both delayed and stopped medication while 9% of members both switched and delayed medication. The data show people who experienced the doughnut hole are 1.3 times more likely to switch, 2 times more likely to delay, 3 times more likely to switch and delay, and 4.7 times more likely to switch, stop, and delay their prescription medications. CONCLUSIONS The results of the study suggest that the doughnut hole is a factor in alteration of prescription fulfillment decisions by Part D members. Because patient non-compliance of medications may result in mortality it is important that the Medicare Part D standard prescription drug plan be designed to limit excessive financial burden to members based on spending levels.