OBJECTIVE: To examine managed-care prescribing patterns for patients beginning pharmacologic treatment in the depressive phase of bipolar. METHODS: This retrospective study (1995-2002) included a cohort of 1203 patients who had 3 consecutive years of data, received an ICD coded diagnosis of bipolar depression and received one of four classes of psychotropic medication (i.e. antidepressant, antipsychotic, benzodiazapine, or mood stabilizer). Treatment patterns were observed for a one-year period post diagnosis. RESULTS: Seventy-seven percent of extracted data was between 1999-2002. Fifty-five different medications were used to create multiple unique mono and/or combination pharmacologic treatments. Nine percent of patients began their treatment in accordance with APA guidelines, whereas, 16% began treatment using only an antidepressant. As switches in treatment occur, use of mono-therapy treatments decrease (-12%) and use of four or more medication combinations increase (+ 9%). One third of patients were treated with four or more medications in combination, at some point, during the year following diagnosis. CONCLUSION: Pharmacologic treatment of bipolar depression is characterized by poly-pharmacy, reflecting the complexity of the disorder; and is often not aligned with guidelines. There is a need to study how these patterns impact service utilization and costs, as well as to further understand the treatment patterns.