Objective.-To determine differences in access to care and medical outcomes for Medicare patients with an acute or a chronic symptom who were enrolled in health maintenance organizations (HMOs) compared with similar fee-for-service (FFS) nonenrollees. Design.-A 1990 household telephone survey of Medicare beneficiaries who reported joint pain or chest pain during the previous 12 months. Sample.-Stratified random sample of HMO enrollees (n=6476) and comparable sample of FFS Medicare beneficiaries (n=6381). Access and Outcome Measures.-Care-seeking behavior, physician visits, diagnostic procedures performed, therapeutic interventions prescribed, follow-up recommended by a physician, and symptom response to treatment. Results.-After controlling for demographic factors, health and functional status, and health behavior characteristics, HMO enrollees with joint pain (n=2243) were more likely than nonenrollees (n=2009) to have a physician visit (odds ratio [OR], 1.19; 95% confidence interval [Cl], 1.03 to 1.38) and medication prescribed (OR, 1.35; 95% Cl, 1:14 to 1.60). Patients with chest pain who were enrolled in HMOs (n=556) were less likely than nonenrollees (n=524) to have a physician visit (OR, 0.50; 95% Cl, 0.30 to 0.82). For both joint and chest pain, HMO enrollees were less likely to see a specialist for care, have follow-up recommended, or have their progress monitored. There were no differences in complete elimination of symptoms, but HMO enrollees with continued joint pain reported less symptomatic improvement than nonenrollees (OR, 0.72; 95% Cl, 0.59 to 0.86). Conclusions.-Reduced utilization of services for patients with specific ambulatory conditions was observed in HMOs with Medicare risk contracts, with less symptomatic improvement in one of the four outcomes studied.