Objective: The current study investigate the immunological reaction state of Th1/Th2 cytokines expression in the peripheral blood mononuclear cells(PBMCs) from patients with lung cancer,and evaluate the effect of astragalus(AG) on it.Methods:The PBMCs from patients were divided into 4 groups:one group as pre-cultured group,and the other cells were cultured with 10%AG,20% AG and without AG (control group) ,respectively.The PBMC from 23 lung cancer patients as well as 19 healthy controls before and after the culture with AG were collected respectively. The Thl/Th2 cytokines expression were detected by RT-PCR considering IFN-r and IL-2 as Th1 cytokines and IL-4,IL-6,IL-10 as Th2 ones. Results:The results showed that the mRNA expression rate of IL-4,IL-6,IL-10 in PBMCs from lung cancer patients was obviously higher than that from the healthy controls( P