In Oriental medicine the primordial Qi and the defensive Qi are considered as important for immunity. Therefore it is anticipated that the improvement of the primordial Qi and the defensive Qi can enhance the ability of immune cells. This experiment was conducted to investigate how Ginseng Radix, Astragali Radix, Atractylodis Rhizoma Alba, Glycyrrhizae Radix, representative of Qi tonifying herbs, affect the immune system in terms of controlling and balancing immune cells. Using the MTS assay, increased proliferations were observed from herbal treated cells, among which Gins-eng showed the highest proliferation. When splenocytes were activated with anti-CD3 plus herbal extracts, levels of IFN-g and IL-4 were increased but those of IL-2 showed little change compared with the control cells. Levels of IL-2, IFN-g and IL-4 were increased in purified CD4 T cells when activated with anti-CD3/anti-CD28 but at $100;{mu}g/ml$ of Astragali and Atractylodis, levels of IL-2 were decreased by 11% and 42%, respectively and those of IFN-g were decreased by 55% and 12%, respectively. Under Th1/Th2 polarizing conditions, levels of IFN-g in Th1 cells treated with herbal extracts were all decreased but when it comes to IL-4, its levels were increased in Ginseng and Glycyrrhizae treated cells but decreased in Astragali and Atractylodis treated cells. Taken together, the data show that compared with other qi tonifying herbs, Ginseng and Glycyrrhizae have a tendency to favor Th2 cell differentiation in vitro.