OBJECTIVE: To examine managed-care treatment patterns for patients diagnosed with bipolar disorder. METHODS: We examined the PharMetrics Integrated Outcomes Database of adjudicated medical and pharmaceutical claims for over 3 million patients from 11 U.S. health plans. We identified 4,455 bipolar patients based on the following criteria: two claims with ICD-9-CM diagnosis for bipolar disorder (296.0, 296.1, 296.4 -296.8), age between 10 and 64, and 1 year of continuous eligibility prior to and following the initial bipolar diagnosis with claims beginning January 1, 1999. RESULTS: Of the 4455 bipolar patients, 80% (3555) received medication-based treatment in a 13-month window around the index diagnosis (12 months post and 1 month pre). A total of 38% of bipolar patients used 4 or more medications during the 13 months. On average each patient underwent 3.6 distinct medication regimens with each, on average, having 2 drugs. Poly-pharmacy (multiple drug combination) treatments represent 60% of the days of treatment and a disproportionate 82% share of costs. Average paid cost per day of treatment for those using poly-pharmacy is $7.56, whereas monotherapy is $2.47. Twenty-three percent of patients are treated with poly-pharmacy initially and permanently. Anti-psychotics and benzodiazapine-based treatments are most commonly seen (80%) in poly-pharmacy treatments. Increasing severity of illness is related to increased poly-pharmacy, with the exception of those patients in remission. CONCLUSION: Pharmacologic treatment of bipolar is challenging, individualized and characterized by poly-pharmacy, reflecting the cyclical nature of the disorder. The impact of the complexity of treating bipolar needs to be studied to determine how service utilization and costs are influenced.