The immunomodulatory effects of exopolymers of Aureobasidium pullulans SM-2001 containing beta-1,3/1,6-glucan were evaluated on the cyclophosphamide (CPA)-treated mice. To induce immunosuppress, 150 and 110 mg/kg of CPA were intraperitoneally injected at 1 and 3 days before start of test material administrations, respectively. Exopolymers were subcutaneously or orally administered in a volume of 10 ml/kg, 4 times; 12-hr intervals from 24 hrs after second treatment of CPA. After treatment of exopolymers, the changes of thymus and spleen weights, splenic amounts of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta and IL-10, thymic and splenic CD3+, CD4+, CD8+ and TNF-alpha+ cells were monitored in CPA-treated mice. As results of CPA treatment, dramatical decreases of the CD3+, CD4+, CD8+ and TNF-alpha+ cells were detected in thymus and spleen with decreases of thymus and spleen weights. In addition, decreases of splenic TNF-alpha, IL-1beta and IL-10 contents were also detected at flow cytometrical observations. However, oral and subcutaneous treatment of exopolymers effectively reduced the immunosuppressive changes induced by CPA. Therefore, it is concluded that exopolymers of A. pullulans can be effectively prevent the immunosuppress mediated, at least partially, recruitment of T cells and TNF-alpha+ cells or enhancement of their activity, and can provide effective prevention or treat regimes for the immunosuppress and related diseases such as cancer, sepsis and high-dose chemotherapy or radiotherapy.