Background : Several studies have suggested that alterations of cytokine level could be related to the pathophysiology of bipolar disorder. In this study, we measured plasma level of Interleukin-12(IL-12), a pro-inflammatory cytokine and transforming growth factor-${eta}$1(TGF-${eta}$1), an anti-inflammatory cytokine before and after treatment in acute manic patients. Methods : The plasma concentrations of IL-12 and TGF-${eta}$1 were measured using quantitative ELISA in 18 bipolar disorder patients and 25 normal controls at admission and 6 weeks later. The psychopathology was measured by Brief Psychiatric Rating Scale(BPRS) and Young Mania Rating Scale(YMRS). Results : IL-12 levels were significantly higher in bipolar manic patients than in controls before treatment. Following the 6-week treatment, the IL-12 level was decreased than before treatment, but sustained still higher level than normal control. TGF-${eta}$1 level was not significant different between manic patients and normal controls before treatment, but was increased after treatment comparing with before treatment in bipolar patients. The ratio of IL-12 and TGF-${eta}$1 was significantly decreased after treatment. Conclusion : Cytokine abnormalities in bipolar disorder might be involved in the pathophysiology of the illness. It is possible that TGF-${eta}$1 plays an important role in the regulation of immunological imbalance in bipolar disorder.