The claim that managed care plans are more efficient than fee-for-service plans has been made so often that it has reached the status of folklore, but the evidence is inconclusive. The claim is usually based on one or both of the following errors: (1) lower medical care costs mean lower total costs (medical plus administrative costs) and (2) lower HMO premiums mean HMOs are more efficient than fee-for-service plans. The first assertion ignores evidence indicating that managed care has driven up administrative costs for both insurers and providers. The second ignores evidence that managed care plans have numerous methods of shifting costs that are unavail-able or less available to fee-for-service plans. The lull in health care inflation duri...