Objectives : This study was performed to evaluate the characteristics of smoking behavior and the effects of smoking on clinical symptoms and level of serum prolactin in schizophrenic patients. Methods : 76 male schizophrenic patients answered the questionnaire about the characteristics of smoking patterns. And patients were assessed by brief psychiatric rating scale(BPRS), positive and negative syndrome scle(PANSS), Hamilton rating scale for depression(HAM-D), assessment for involuntary movement scale(AIMS) and symptom checklist 90 R(SCL-90-R). Serum prolactin levels were measured by enzymeimmunoassay. Results: 1) The frequences of drinking coffee were significantly higher in smokers. The reasons for smoking were to relieve tension, to avoid boredom, due to habit and to do with friends. 80.1% of smokers tried quitting, but smoking was relapsed due to craving and withdrawal symptoms. 2) No significant difference was seen in mean neuropeltic doses, scores of PANSS and AIMS. But as for BPRS, scores of anxiety/depression subscale were significanly lower in smokers. Scores of HAM-D and scores of interpersonal sensitivity and phobia among SCL-90-R were significantly lower. 3) Levels of serum prolactin were significanlty lower in smokers. Conclusion : These findings suggest that in schisophrenia smoking relieves anxiety and depression subjectively But decreased prolactin levels may suggest that the possibility of increased dopamine in CNS.