Data from a 6-year follow-up period were used to analyze the mortality of adults who had been continuously enrolled in a prepaid group practice health maintenance organization (HMO) for the previous 7 years. Thirteen percent of the HMO members were classified as consistently high users of outpatient care. Even after adjustment for age, sex, and cigarette smoking, this high user group's mortality rates during the follow-up period were significantly greater than those of the other HMO enrollees. The HMO members as a whole had mortality rates marginally lower than the mortality of the general Oregon population. It can be concluded that HMO enrollees who consistently use high quantities of health care resources generally have significant medical problems in addition to psychosocial difficulties. Assuming that mortality reflects health, long-term HMO members as a group are not much healthier than ordinary Oregonians.