Background: Hyperlipidemia and overweight are more common problems in schizophrenic patients. In several studies showed the mortality in schizophrenic patients more than the general population. One of the most common problems is overweight. Body mass index (BMI) more than 30 is also associated with the use of antipsychotic drugs in patients. This study was assessed to understand the association between BMI and demographic and clinical factors such as sex, age, education, and used drugs in schizophrenia patients. Methods: In descriptive study, 160 patients with detected schizophrenia were studied. In this study the frequency distribution of BMI was investigated. The data analyzed with SPSS soft ware and chi- square and ANOVA tests. Findings: Twenty percent patients had a BMI under normal value, 41.9% had normal BMI, 46.3% were overweight, and 11.9% were fat. The results showed a significant relation between BMI and sex (P = 0.03). Conclusion: This study showed that BMI in schizophrenic patients, especially in women, is more than normal population. But age, type of drugs, and education does not affect BMI. Because of more BMI than normal population, we must apply an effective activity to control weight in schizophrenia patients. Key words: Body mass index, Schizophrenia, Demographic and clinical aspects.