GAO discussed Medicare beneficiaries' access to quality care in health maintenance organizations (HMO), focusing on the Health Care Financing Administration's (HCFA): (1) monitoring of HMO compliance with quality standards; (2) enforcement actions when HMO fail to comply with these standards; and (3) implementation of beneficiaries' right to appeal HMO denials of care. GAO noted that: (1) although HCFA routinely reviews HMO operations for quality, these reviews are generally perfunctory and do not assess the financial risks HMO transfer to providers; (2) HCFA collects insufficient data on HMO services to identify providers who may be underserving Medicare beneficiaries; (3) HCFA has been reluctant to take strong action against HMO who fail to comply with Medicare standards; (4) HCFA allows 6 months or more to resolve disputes about HMO denials of care, which can create uncertainty or high costs for beneficiaries; and (5) private sector strategies to ensure good HMO performance provide models for improving federal oversight of Medicare HMO.