This study investigated the health care costs for schizophrenic patients while documenting the relationship between health care costs and the patient's use of antipsychotic medications. METHODS: Paid claims data from the Medi-Cal program were used to identify schizophrenic patients with a minimum of 1 year of data available for analysis (N=2,680). Patients were divided into treated and untreated populations based on their purchase of at least one prescription for an antipsychotic medication during the year. Drug use patterns for treated patients documented the extent to which patients delayed drug therapy or switches in drug therapy occurred during the first year. Multivariate logistic regression models were estimated to investigate the factors related to delays in therapy or switching therapies. OLS regression models were used to estimated the health care costs associated with these drug use patterns. RESULTS: Direct health care cost per schizophrenic patients averaged $24,000 per year. Nearly 21% of schizophrenic patients used no antipsychotic drug therapy for up to one year which was not associated with increased costs. Over 27% of treated patients delayed treatment resulting in increased costs of between $3,262 (p<.08) and $6,189 (p=<.01). 41% of treated patients with no delays in therapy switched therapy within 1 year at a cost of approximately $8,000 (p<.01). Only 11% of treated patients consistently purchased antipsychotic medications during the first year. However, long term use was not associated with lower costs. An intent-to-treat analysis failed to document any differences between medications. CONCLUSIONS: Schizophrenia patients consume significant health care resources. Medications used to treat schizophrenia did not differ in terms of duration of therapy or impact on total health care costs.