Objectives : To evaluate experimentally the clinical effect of Bojeongjeongcheon-tang, we observed the cytokines ($IL-1{eta}$, IL-4, IL-5, IL-6, IL-10, TNF-{alpha},{;}TGF-{eta},{;}IFN-{gamma}$) and what effect they have on IgE in B cells of a rat. Methods : First of all, we extracted the spleens of healthy Balb/c mice and separated B cells from them. These B cells were cultured with anti-CD40 mAb (500 ng/ml), rmIL-4 (500 U/ml), Bojeongjeongcheon-tang (100 ug/ml, 10 ug/ml, 1 ug/ml). We used rmiL-10 (50 ng/ml) as a control group. Furthermore, we analyzed the expression of IgE, CD23, CD69 and the coherence of HRF in B cells using a flow cytometer. We also analyzed the cytokine gene expression in B cells by reverse transcriptase-PCR. We also measured B cells proliferation using the Liquid Scintillation Counter. Results : In this study, the Bojeongjeongcheon-tang treated group showed a tendency to decrease depending on the density compared with the control group in the expression of IgE+, CD23+, CD69, HRF. All of the Bojeongjeongcheon-tang treated group showed inhibitory effects with $IL-1{eta}$, IL-4, IL-5 and proliferating effects with IL-6, IL-10, and $IFN-{gamma}$ on cytokines transcript expression depending on the density. Meanwhile, $TNF-{alpha}$ increased in all density. In IgE production, there was inhibitory effect on Bojeongjeongcheon-tang (both 100 ug/ml and 10 ug/ml) of significance (p < 0.01, p < 0.05). Also in B cell proliferation, the result revealed an inhibitory effect of Bojeongjeongcheon-tang (both 100 ug/ml and 10 ug/ml), of significance (p < 0.001, p < 0.01). Conclusions : This study shows that Bojeongjeongcheon-tang has an inhibitory effect on the production and activity of B cells. Also it inhibited CD23, IL-4 activity and IgE production and activation. It is obvious that Bojeongjeongcheon-tang treats asthma by inhibiting the production of histamine and HRF, IL-5 and proliferating IL-10. Also Bojeongjeongcheon-tang has some preventive effects on bronchial change by inhibiting $TGF-{eta}$, which stimulates the bronchial transformation.