The growth of managed care has prompted questions about the effects of health maintenance organizations (HMOs) on consumers. This Issue Brief reports the results from a large national study of the privately insured population. No detectable difference was found between HMOs and other types of insurance in the use of three costly services--inpatient care, emergency room use and surgeries--and differences in reports of unmet need or delayed care are negligible. Differences for other measures pose a trade-off for consumers: HMOs provide more primary and preventive services and lower financial barriers to care, but they provide less specialist care and raise administrative barriers to care. In addition, patients in HMOs report less satisfaction, less trust in physicians and lower ratings of physician visits. These findings have implications for the current policy debate about managed care.