OBJECTIVES: This article describes the process through which the MMC survey was developed and examines issues in using this survey with Medicare beneficiaries that have implications for all CAHPS surveys. These include the ability of Medicare beneficiaries to use MMC navigational features, whether access measures are meaningful for this population, and whether beneficiaries' familiarity with managed care influences their health plan assessments. BACKGROUND: The Health Care Financing Administration (HCFA) is mandated to provide comparative plan information, based partly on consumer surveys, to Medicare beneficiaries. The Consumer Assessments of Health Plans Study (CAHPS) is an integrated set of tested, standardized surveys of health plan enrollees. To meet its goal, HCFA has invested in the development of a CAHPS survey of beneficiaries enrolled in Medicare Managed Care plans (MMC). METHODS: Cognitive interviews were completed with 31 Medicare beneficiaries. A field test also was conducted with beneficiaries to examine patterns of survey response. A sample of 956 eligible individuals was selected from six health plans. Using a combination of mail and telephone data collection, 663 (69%) questionnaires were completed. This article provides selective results from these tests. RESULTS: The use of screening questions, skip instructions, and tailored 'not applicable' response options appeared to facilitate the response task. Some CAHPS access questions were not meaningful to Medicare beneficiaries. The data do not support the need to adjust for length of plan enrollment. CONCLUSION: Analyses suggested changes to improve the MMC survey and to make other CAHPS surveys consistent with these changes