Ethnicity may influence treatment decisions in mental disorders. We undertook a survey of the prescribing of antipsychotics for in-patients in three south London mental health trusts. A total of 255 patients (152 White, 103 Black) were included. Median dose of antipsychotic (% of licensed dose) was 58.3% for White and 50.0% for Black patients (adjusted effect size=0.14, 95% CI −0.34 to 0.63). High-dose antipsychotics were prescribed to 15.1% of White and 11.7% of Black patients (adjusted odds ratio (OR)=0.5, 95% CI 0.19–1.33), and antipsychotic polypharmacy was recorded for 25.7% and 31.1% respectively (adjusted OR=3.05, 95% CI 1.44–6.46). Prescribing quality was similar for Black and White patients.