Bipolar disorder is a severe and costly condition that accounts for approximately $7.6 billion in direct health care costs in the US. Atypical antipsychotics are increasingly being used for the treatment of Bipolar disorder. OBJECTIVE: We conducted a retrospective study to determine whether there are differences in resource utilization and cost of care between patients with bipolar disorder receiving risperidone, olanzapine or quetiapine. METHODS: In June 2001, 573 persons reported being diagnosed with bipolar disorder on a self-administered questionnaire. We compared the utilization of inpatient and outpatient services as well as mental health-specific resources by patients receiving risperidone, olanzapine, or quetiapine over the previous six months. Drug costs were not included in the analysis. A regression model was used to control for use of other drug classes. National cost multipliers published by the U.S. Census Bureau, 2000, were used to calculate the cost of care. RESULTS: Out of the 573 respondents, 108 had sufficient information on resource utlization for analysis. When controlling for use of other drug classes, the olanzapine group (n=48) had a higher utilization of outpatient services (p=0.008) compared to risperidone (n=31). The risperidone group also had lower utilization of inpatient and outpatient services compared to quetiapine (n=29), but the differences were not statistically significant. The cost of care for all services was $8579, $4349, and $5221 for olanzapine, risperidone, and quetiapine, respectively, while the cost of mental health services was $6186, $2775, and $4022, respectively. CONCLUSION: Patients with bipolar disorder receiving risperidone appear to have lower utilization of healthcare services and lower costs of care.