OBJECTIVES: To illustrate the decrease in resource utilization over time among persons with bipolar disorder treated with antipsychotics. METHODS: In December 2000, 234 persons reported a diagnosis of bipolar disorder on a self-administered questionnaire. Of these, 57 reported currently using an antipsychotic: Haldol, Risperdal, Seroquel, and Zyprexa. Respondents using antipsychotics were categorized according to the number of months on drug: zero to six and seven or greater. The treatment-duration groups were compared by resource use during a six-month period: number of visits to all outpatient providers, including primary physician, counselor, gynecologist, neurologist, psychiatrist, psychologist, and other medical specialists; visits to the emergency room for mental health reasons; days hospitalized for mental health reasons. Lastly, costs of resources used were calculated based on US Census Bureau, Statistical Abstracts of the United States, 2000: emergency room costs, $320 per visit; hospitalizations, $1,126 per day; outpatient provider costs, $85 per visit. RESULTS: Respondents using antipsychotics for seven months or longer had fewer visits to outpatient providers (17.1 versus 30.9, p = 0.086), emergency room visits (0.2 versus 0.7, p = 0.062) and days of hospitalization (1.6 versus 3.8, p = 0.202) than those using an antipsychotic for six months or less. Among respondents using an antipsychotic for seven months or longer, the average cost of outpatient resource use ($1453.23 versus $2623.91), ER visits for mental health reasons ($70.00 versus $208.70), and hospitalization for mental health reasons ($1816.13 versus $4299.27) are lower than among those using an antipsychotic for six months or less. CONCLUSION: Resource utilization, especially hospitalization, during the early months of antipsychotic use is very costly. However, continued use of an antipsychotic leads to a decrease in inpatient and outpatient resource utilization. Therefore, it becomes more cost-effective to maintain a patient on antipsychotic medications over time.