On behalf of the Centers for Medicare and Medicaid Services (CMS), AIR studied the reasons why Medicare beneficiaries without creditable coverage do not enroll in Part D and how they can be encouraged to do so. The project consisted of a survey of beneficiaries without creditable coverage or Part D plans and interviews with health professionals. The survey identified factors that were associated with lack of prescription drug coverage among Medicare beneficiaries and potential approaches to providing additional information about Part D enrollment. The data were used to identify three distinct segments in this population. The second phase of the study involved in-depth interviews with physicians, pharmacists, and the staff of medical practices and pharmacies to assess the feasibility of engaging them as information intermediaries about Part D enrollment for Medicare beneficiaries. These three tasks enabled AIR to assess the effectiveness of current information that CMS provided about Part D and make recommendations on strategies that would engage more providers and beneficiaries.