OBJECTIVE: To describe and compare treatment patterns of patients with schizophrenia/schizo-affective disorder across 15 different countries. METHODS: Examination of baseline data from a prospective, multi-centre, double-blind, randomised comparison of quetiapine and chlorpromazine. 381 patients were recruited from 12 European countries plus Canada, Australia and South Africa. An economic assessment (Client Services Receipt Inventory) included questions about health service use in the 3 months prior to assessment and was adapted as far as possible to obtain internationally comparable information. Analyses are on country-level data, irrespective of treatment group. RESULTS: Overall, 62% of patients had a diagnosis of paranoid schizophrenia. Mean patient age for each country ranged from 27 to 40 years and the proportion of males ranged between 0-85%. There were notable variations in service use. The proportion of patients in each country who reported using any health services ranged between 69-100%. There was a large variation in the proportions using inpatient services (range 23-100%) and average length of stay (range 7-76 days). Take-up of community-based services also differed across countries: 0-75% seeing community psychiatric nurses, 0-46% seeing social workers and 0-75% seeing a general practitioner. Graphical representation of treatment patterns using starplots showed striking similarities between Australia and the UK; and Canada and Norway. CONCLUSION: The pre-treatment baseline data are of interest in their own right as they provide a unique opportunity to examine existing treatment patterns across a large number of countries. Sources of treatment variation across countries can be numerous and complex, depending on national, local and patient level factors. Such international variations should lead us to question whether results from a study conducted in one country can easily be used to inform mental health purchasing decisions in another.