Most prescription pattern surveys have found a high rate of antipsychotic polypharmacy. To date few studies have investigated antipsychotic polypharmacy in Chinese patients with schizophrenia in general and outpatients in particular. This study examined the frequency and sociodemographic and clinical correlates of antipsychotic polypharmacy in Hong Kong (HK) and Beijing (BJ), China. Three hundred and ninety-eight clinically stable outpatients with schizophrenia were randomly selected and interviewed in HK and BJ using standardized assessment instruments. Antipsychotic polypharmacy was found in 17.6% ( N=70) of the whole sample and in 28% and 7.1% of the HK and BJ samples, respectively. Polypharmacy was associated with monthly income, severity of negative symptoms and extrapyramidal side effects (EPS), use of depot antipsychotic and anticholinergic drugs, doses of antipsychotics, and the number of hospitalizations. In multiple logistic regression analysis, younger age, number of hospitalizations, site (HK vs. BJ), and the use of depot antipsychotics were all significantly associated with antipsychotic polypharmacy. Although the ethnic and clinical characteristics of the two cohorts were nearly identical, there was a wide variation in the prescription frequency of antipsychotic polypharmacy between HK and BJ, suggesting that sociocultural and economical factors and traditions of psychiatric practice all played a role in determining antipsychotic polypharmacy. Clinicians should bear in mind that, at least for clinically stable patients, no scientifically sound therapeutic principles for antipsychotic polypharmacy exist.