Abstract: Objective To observe the influence of electromagnetic irradiation on Th1/Th2 cytokine balance.Methods The mice were continuously exposed to 5 mW/cm² electromagnetic wave 30 min/day for 30 days.The expression levels of interferon-gamma(INF-γ) and interleukin-4 (IL-4) were detected with reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA).The excursion of Th1/Th2 cytokine balance induced by electromagnetic irradiation was analysed.Results The INF-γ expression level was increased by 5 mW/cm² electromagnetic irradiation.At the 8th day of the electromagnetic irradiation,the INF-γ level in murine serum was increased by 27.84% compared with that of the sham group(P< 0.05).The IL-4 expression level showed a decrease tendency after the electromagnetic irradiation but the decrease was not significant compared with that of the sham (P> 0.05).Conclusion The 5 mW/cm² electromagnetic irradiation can lead the deflection of Th1/Th2 cytokine balance to Th1.