OBJECTIVE: To analyse by geography, in this case by state, the usage patterns of the different antipsychotic medications purchased by public and private hospitals in Australia. METHODS: National hospital sales data for all antipsychotic medications purchased by 565 hospitals were obtained from IMS Health Australia for the period January 2004 to December 2004. This was segregated into the major states and territories of Australia (New South Wales, Northern Territory, Queensland, South Australia, Tasmania, Victoria & Western Australia). This was then converted into defined daily doses (DDDs) for each agent. The level of antipsychotic use in each state was expressed as the estimated DDDs per 1000 population/day. RESULTS: Significant variation by state was seen in the usage of antipsychotics across Australia. Nationally the atypical antipsychotics were the most frequently used class of agents, accounting for 69% of total use. The use of individual atypical agents varied significantly across geographies. Clozapine use varied from a high of 42% in Victoria to 13% in SA and WA. Depot typical antipsychotics were the most commonly used class of agents (39%) in NT, whereas they only accounted for 15% of use in Victorian hospitals. Oral typical agents were most frequently used in SA (17%) and least used in WA (6%) and Vic (7%). CONCLUSIONS: Significant variation in antipsychotic usage patterns by hospitals is seen between the different states in Australia. Community usage patterns, by comparison, show much less variation. Such information has the potential to be used as an indicator of quality of care in mental health services.