Objective: To examine the prevalence of metabolic syndrome and its risk factors in a large group of schizophrenic patients. Methods: Sociodemographic and treatment data were collected from medical records of 1,103 inpatients and outpatients treated for schizophrenia at Seoul National Hospital in Seoul, Korea. Anthropometric measurement and blood testing were conducted for collection of physical and biochemical data and diagnosis of metabolic syndrome. Data for metabolic syndrome prevalence were compared by sex, age, metabolic syndrome markers present, treatment of markers, and types of antipsychotics and individual drug agents used. Results: Mean prevalence of metabolic syndrome in all subjects was 43.9% and 40.1% according to adapted Adult Treatment Panel III (ATP-IIIa) and International Diabetes Federation criteria, respectively. No significant differences were found in prevalence according to ATP-IIIa criteria between men (42.6%) and woman (45.9%). A trend toward higher prevalence with age was observed for both sexes until 50 years, followed by a continued increase for women but a decrease for men. Use of a combination of atypical antipsychotics was associated with the highest metabolic syndrome prevalence and use of aripiprazole with the lowest. High percentages of subjects with hypertension and dyslipidemia were not being treated for these conditions. Conclusion: Despite their higher prevalence in schizophrenic patients, metabolic syndrome and its markers are not being adequately managed in these patients. Treatment of schizophrenic patients requires attention to not only their psychiatric conditions but also associated medical conditions by individual health care practitioners and hospitals as well as the public health care sector as a whole.