OBJECTIVE: Studies of how differences in systems of care, including cultural differences, affect prescribing practice and patient outcomes are important and can help answer questions such as the effectiveness of clozapine in routine practice. This study examined the use of clozapine in Maryland and in Victoria, Australia. METHODS: This study used medical record data to examine the use of clozapine in January 2000 for people with schizophrenia in two different countries. Data were gathered from all six public inpatient facilities in Maryland and from the two main community outpatient centers in Victoria. Outpatients were studied in Victoria because Australia's inpatient mental health facilities have closed and people with treatment-resistant schizophrenia are managed exclusively as outpatients. RESULTS: In Maryland 591 inpatients with schizophrenia were given a prescription for second-generation antipsychotics; in Victoria 356 outpatients with schizophrenia were given such a prescription. Among second-generation antipsychotics, clozapine was used significantly more frequently in Australia than in Maryland for the treatment of schizophrenia (173 prescriptions, or 49 percent, compared with 144 prescriptions, or 19 percent). Both systems used clozapine mostly for the treatment of schizophrenia (94 percent in Victoria compared with 88 percent in Maryland). The mean clozapine dosages that were used for the treatment of schizophrenia were significantly higher in Maryland than in Australia (522 mg per day compared with 431 mg per day). CONCLUSIONS: Significant differences in use and dosages of clozapine were found in two populations that were similar in diagnoses and demographic characteristics.