Objective : It is well known that modern chemotherapy against cancer has side effects to a living body, especially hemopoietic and immunologial disfunctions. However, there are no effective ways to reduce them. Recently, traditional Korean herb medicine has been reported to have some biological modifying responses. Therefore, we hypothesized that additional application of herb medicine during chemotherapy is more effective to reduce its side effects. While we were studying the effects, we have observed the inhibitory effect of Soamgudamikgitang on formation of side effects derived from Cyclophosphamide, it has been used in clinical practice at Kyung Hee Medical Center. Methods : We injected 200mg/kg of Cyclophosphamide, one time, to an experimental group, consisting of ten mice. We divided them into eight groups: normal, CPX, SAKT 2mg, SAKT 10mg, SAKT 50mg, SAKT 2mg, CPX, SAKT 10mg+CPX, SAKT 50mg+CPX. We injected Soamgudamikgitang seven days, five days, three days, and one day before we injected CPX. One day, three days, and five days after CPX injection, we injected Soamgudamikgitang again and then killed all the mice. The parameters determined in this experiment were daily body weight liver and spleen weight, RBC, WBC, and platelet for hemopoietic dysfunction and AST, ALT for hepatotoxicity, BUN, creatine for renal toxcity, lymphocyte proliferation activity and lymphocyte subsets for immunological toxcity. Results : We have found that Soamgudamikgitang has inhibitory effects on the formation of Cyclophosphamide's side effects. Significant differences between the group, which contained Cyclophosphamide, and the other group, which contains Cyclophosphamide and 2, 10, 50mg of Soamgudamikgitang respectively were observed. Platelets(2mg of Soamgudamikgitang, p<0.05 ;10mg, p<0.01 ;50mg, p<0.001), liver weight(50mg, p<0.01), spleen weight(10mg, p<0.05), AST(all groups, p<0.01), ALT(2mg, p<0.01 ;10mg, p<0.05 ;50mg, p<0.01), BUN(2mg, p<0.01 ;50mg, p<0.05). Although immunological in both lymphocyte proliferation and its subsets were not observed, which shows that Soamgudamikgitang has a strong effect on T cell activities. Conclusions : From the above results, we can expect that the combined therapy of Soamgudamikgitang and Cyclophosphamide is more effective for treating cancer patients.