OBJECTIVES Atypical antipsychotics are currently the most frequently prescribed class of drugs for schizophrenia. These drugs appear to be associated with varying degrees of metabolic adverse effects. We conducted a retrospective clinical study to evaluate the adverse metabolic effects of antipsychotic medications in schizophrenic patients in Taiwan population. METHODS This is a retrospective observational study. A total of 431 outpatients who were diagnosed with schizophrenia and taken clozapine or olanzapine or risperidone or haloperidol for more than one year were included in this study. We excluded those who took other drugs known to affect glucose metabolism (including á, â-blockers, thiazide diuretics, phenytoin, valproate, and corticosteroids), and those who were diagnosed with diabetes mellitus and hyperlipidemia at the initial time of study. The changes of blood lipids and fasting blood glucose levels noted in the medical records were reviewed and analyzed. RESULTS The results indicated that 298 outpatients showed weight gain after 6~8 months of medications. 83.3%(60/72) of risperidone-treated patients had experienced significant weight gain as compared with 48.8%(40/82) of clozapine and 4% (2/50) haloperidol treated patients (p<0.001).The potential risk of increased fasting blood glucose, cholesterol, and triglyceride levels for risperidone-treated patients were 50.5 ± 4.2%, 13.9 ± 5.6% and 53.8 ± 4.2%, respectively. 48 patients need additional drugs to regulate the increased metabolic levels, such as atorvastatin for increased triglyceride levels and glucophage for increased blood glucose level. The extra medications expenditure used to regulate the adverse effect was about NT 13 million each year. CONCLUSIONS The atypical antipsychotic drugs can cause adverse metabolic effects. American Diabetes Association (ADA) suggested to monitor patients' body weight, fasting blood glucose, and lipid profile for those who are prescribed atypical antipsychotics. Additionally, the diet control and regular exercise should be suggested to patients who have already been getting weight in the treatment of atypical antipsychotics.