Abstract We examined patterns of care for 1246 adults treated for bipolar disorder in a large health maintenance organization. Computerized pharmacy and visit data were used to identify patients treated for bipolar disorder. Automated medical records for the following year were used to assess continuity and dosing of treatment with mood stabilizers, laboratory monitoring for adverse effects and therapeutic serum levels, and frequency of follow-up visits. Of our 1246 subjects 83% filled a mood stabilizer prescription during the 1-year study period, and doses were within recommended ranges 80% of the time. Over 75% of the patients on mood stabilizers had at least one apparent interruption in medication use. Approximately half of the long-term users of mood stabilizers had at least one 7-month period without a recorded blood level and approximately half had a similar period without monitoring for adverse medication effects. Of the 116 subjects discharged from a psychiatric hospitalization 58% had a visit with a psychiatrist or a psychiatric nurse practitioner within 30 days. Of those discontinuing mood stabilizer treatment 68% made a mental health visit within 90 days. Our findings demonstrate the feasibility of using administrative data systems for population-based quality of care assessment and suggest opportunities for improving the care of bipolar patients.