Lack of coverage, knowledge, and physician guidance, and low socioeconomic status are major barriers to receiving preventive care. Compared with fee-for-service insurance, managed care promotes prevention through more generous coverage, physician incentives, and patient education, and members of MCOs use more preventive services than do members of fee-for-service plans. However, cost effectiveness of prevention has not been previously examined. A study of seven preventive services suggests that managed care enrollees more frequently obtained four preventive services, including two less-effective ones. For less-effective services, it may be prudent to base disease-risk assessment on key factors other than age and sex, and screen only patients at high risk. Effective screening strategies must be identified, especially for the underserved, low-income population.