Systematic experiments on the effects of He-Ne laser irradiation combined with the traditional antitumor medicine of cyclophosphamide on peripheral blood serum IgG were conducted by using the experimental model of mouse S180 ascites sarcoma. Three groups of tumor bearing mice were irradiated upon the inner corners with the dosages of 11 00, 14 67 and 22 00 J/cm 2 He-Ne laser irradiation respectively, and injected with CYT intraperitoneally to observe the changes of peripheral blood serum IgG in tumor bearing mice. The values of peripheral blood serum IgG in tumor bearing mice in the mice with CYT+He-Ne laser irradiation treatment were higher than that with CYT treatment only. The kinetic detection of peripheral blood serum IgG indicated that CYT showed the immunosuppressive effects on the tumor bearing mice, and the immunosuppressive effects were alleviated in some degree by He-Ne laser irradiation.