Criteria used in this study established that 13% of long-term adult members of a prepaid group practice health maintenance organization (HMO) were consistently high users of outpatient medical care services. This population accounted for 31% of the total doctor office visits (DOVs), 35% of the hospital admissions, and 30% of the outpatient surgical services for long-term members. The most frequent reason for DOVs in this high user group was treatment and/or follow-up of chronic conditions. Patterns of utilization were unrelated to marital status, income, occupation, and perceived social class. Smoking and alcohol use also were not associated with utilization patterns. However, the consistently high users were more likely to perceive their health status as fair or poor and to report a higher number of physical symptoms. They were also more likely to be characterized by a higher degree of psychological distress, especially depression. Contacts with the HMO's mental health department constituted less than 1% of their total medical care contacts, and only 13% made at least one mental health contact over the study period. The findings are discussed in terms of their health and medical care implications.