Health-maintenance organizations (HMOs) are accountable for the preventive care of approximately one quarter of the U.S. population, and public health agencies have an increasing role in assessing the quality of care for populations enrolled in HMOs. The Health Plan Employer Data and Information Set (HEDIS 3.0) reports on the performance of HMOs and is sponsored and maintained by the not-for-profit National Committee for Quality Assurance (NCQA). This report summarizes state-specific HEDIS estimates for the delivery of four clinical preventive services: screening mammography and Papanicolaou (Pap) tests for women, screening retinal examinations for persons with diabetes, and advising smokers to quit. The advice-to-quit-smoking data from 12 states represented by HEDIS is then compared with data on insured respondents from the corresponding 12 states surveyed by the Behavioral Risk Factor Surveillance System (BRFSS). These findings underscore the potential public health importance of HEDIS data (e.g., creating the capacity to assess statewide prevention interventions) and highlights some of the methodologic issues of comparing performance measures from HEDIS to the BRFSS.