Objective To explore the clinical significance on peripheral blood Th1/Th2 related cytokines both before and after treatment in patients with bronchial asthma. Methods Serum IL-2(with RIA), serum IFN-γ,IL-4, IL-10(with ELISA) levels were determined in 31 patients with bronchial asthma and compared to 35 normal controls. Result Before treatment, serum IL-2,IFN-γ, levels showed significantly lower than those in controls(P<0.01) ,but serum IL-4, IL-10 levels were significantly higher(P<0.01) , after treatment for 1 month, the levels expressed significant no difference( (P>0.05). Conclusion Existence of with bronchial asthma imbalance of Th1/Th2 cell immunity in patients with bronchial asthma and furthermore, the hypofunction of Th1 cell immunity, down - regulated IFN-γ may play an important role in the pathogenesis of asthma, it is a negative regulative effect on the development of asthma. Meanwhile, there is a hyperfunction of Th2 cell immunity. IL-4, IL-10 representing. Th2 cell immunity may play a positive promoting inflammatory effect on the development of bronchial asthma in children.