To determine whether consumers find the care provided by health maintenance organizations (HMOs) and that provided in the fee-for-service (FFS) system equally acceptable, the authors randomly assigned 1,537 people ages 17 to 61 either to FFS insurance plans that allowed choice of physicians or to a well-established HMO. They also studied 486 people who had already selected the HMO (control group). Those who had chosen the HMO were as satisfied overall with medical care providers and services as their FFS counterparts. The typical person assigned to the HMO, however, was significantly less satisfied overall relative to FFS participants. Attitudes toward specific features of care favored both FFS and HMO, depending on the feature rated. Four differences (length of appointment waits, parking arrangements, availability of hospitals, and continuity of care) favored FFS; two (length of office waits, costs of care) favored the HMO. HMO vs. FFS differences in ratings of access to care and availability of resources mirror differences in the organizational features of these two systems that are generally considered responsible for the significantly lower medical expenditures at HMOs. Regardless of their origin, less favorable attitudes toward interpersonal and technical quality of care in the HMO have marked consequences: dissatisfaction and disenrollment.