OBJECTIVE: For decades, lithium has been prescribed to treat bipolar disorder. Its efficacy has been documented by clinical trials and by data from specialized clinics. An issue of considerable interest is the use of lithium in managed care systems. This project examined the use of lithium and its continuity of use by enrollees of a health maintenance organization (HMO). METHOD: In a 6-year longitudinal cohort study, 1,594 lithium users aged 15 years and older who were enrolled in an HMO were followed from 1986-1991. Data were obtained from automated databases and from medical record review of a random 5% subsample of the group (N = 74). RESULTS: Bipolar disorder was the most frequent morbidity treated. Eighty-four percent (N = 62 or 74) received services from a psychiatrist. Annual prevalence of lithium use increased over the 6-year period from 1.4 to 2.3 persons per thousand HMO members. Duration of use varied widely with some long-term but many short-term users. Discontinuation of treatment was associated with evaluated rates of psychiatric hospitalization and use of psychiatric emergency services. Lithium users were much more likely to receive a variety of other psychotropic drugs than nonusers of the same sex and age. CONCLUSIONS: Lithium use in this population was more often sporadic than continuous. Discontinuation of lithium was associated with psychiatric hospitalization. If lithium is to be a cost-effective treatment for bipolar disorder, managed care systems will need to improve adherence to drug treatment regimens.Abstract Teaser