Objectives : The water extract of Bowon-tang composited with the Panax, Astragalus and Glycyrrhiza Radix has been traditionally used for treatment of a sickly child and smallpox in oriental medicine. However, little is known about the regulatory effects of Bowon-tang on the production, expression and activity of immune mediators [nitric oxide, prostaglandin E 2 , inducible nitric oxide synthetase, cyclooxygenase-2], the macrophage activation factor production, the proliferation, subset expression, the killing activity, and the capping in immune cells.Methods : In this study, we investigated the effects of water extracts from Bowon-tang, Panax, Astragalus or GR in mouse immune cells or human Jurkat T cells.Each extract (25-200 ㎍/㎖) per se had no cytotoxic effect in unstimulated macrophages, but concentration-dependently regulated NO and PGE 2 production, iNOS expression, and COX-2 activity in mouse peritoneal macrophages with MAF stimulation. These regulatory effects were synergistically increased by their combination (Bowon-tang).Results : The extract of Bowon-tang concentration-dependently regulated T cell proliferation, CD4 + and CD8 + expression, and NK killing activity in mouse splenocytes and capping in Jurkat T cells. Conclusions : These results suggest that the water extract of Bowon-tang composited with the Panax, Astragalus and GR may be useful for therapeutic drugs against a sickly constitution and immune diseases, probably by regulating the production of immune mediators.