OBJECTIVE: To examine physicians' attitudes about the impact of Medicare Part D and how it varied among seniors, particularly Medicare-Medicaid dual-eligible enrollees. STUDY DESIGN: Web-based survey of primary care physicians in North Carolina (generous Medicaid formulary) and Florida, Massachusetts, and Texas (restrictive Medicaid formularies). METHODS: Of 5141 eligible primary care physicians, 716 (14%) responded between November 2007 and March 2008. We examined Part D's effects on access overall and for selected populations. We used descriptive and regression analyses to assess physicians' views about Part D's effects on dual-eligible enrollees and how those views differed between North Carolina and the other states. All analyses were weighted for nonresponse. RESULTS: More respondents had a favorable (48%) than an unfavorable (37%) view of Part D overall, and 55% reported Part D improved access to prescription drugs in general. However, 44% reported access declined for individuals with prior drug coverage, and 64% reported Part D formularies were insufficient for their patients' needs. Nearly half (49%) reported dual-eligible enrollees' access was worse under Part D in 2007 relative to Medicaid before 2006; 63% reported higher administrative burden. Physicians reported Part D lowered dual-eligible enrollees' access and increased providers' burden more in North Carolina than in the 3 restrictive Medicaid states. CONCLUSION: Primary care physicians held generally positive but widely varying views of Part D. Respondents expressed concerns about access to prescription drugs under Part D, particularly for dual-eligible enrollees. Improving the transparency and generosity of Part D formulary coverage may improve access.