BACKGROUND: Several reports have suggested that cytokine alterations could be related to the pathophysiology of schizophrenia. In this study, we measured plasma level of interleukin-12(IL-12), a pro-inflammatory T helper 1(Th1) cytokine and transforming growth factor-beta1(TGF-beta1), an anti-inflammatory Th3 cytokine before and after antipsychotic treatment in schizophrenic patients. METHODS: The plasma concentrations of IL-12 and TGF-beta1 were measured by using quantitative ELISA in 23 schizophrenic patients and 31 normal controls at admission and 8 weeks later. The psychopathology was measured by Brief Psychiatric Rating Scale(BPRS). RESULTS: IL-12 and TGF-beta1 levels were significantly higher in schizophrenic patients than in controls before treatment. At the 8 week of treatment, the TGF-beta1 levels returned to control values, while IL-12 levels were not significantly changed. There were no significant correlations between the changes of BPRS scores and the changes of IL-12 or TGF-beta1 levels in schizophrenic patients. CONCLUSION: Cytokine abnormalities in schizophrenia might be involved in the pathophysiology of the illness. It is possible that TGF-beta1 plays an important role in the schizophrenia.