Many purchasers and consumers of health care have become concerned about the quality of care being delivered in managed care plans. Little is known, however, about the health plan characteristics that are associated with better performance. We used survey responses from 82,583 Medicare beneficiaries from 182 health plans to study the association of consumers' assessments of care with health plan characteristics. For-profit and nationally affiliated health plans received much worse scores on the outcomes of interest, particularly for overall ratings of the health plan and composite measures of customer service and access to care. Health plans accredited by the National Committee for Quality Assurance did not receive higher scores.