Twenty mg of sizofiran (Schizophyllum glucan: SPG) was i.m. administered one day prior to surgery, or the same dose was injected 8 days and one day before surgery to 40 patients with cervical cancer and 15 with a benign tumor. Frozen sections of fresh pelvic lymph nodes from these patients obtained during surgery were stained by the ABC (Avidin-biotin-peroxidase complex) method with several monoclonal antibodies to define the surface phenotype of mononuclear cells. SPG led to a great increase in the number of cells stained with interleukin-2 receptor (IL-2R) and Leu 3a antibodies, mainly in PC, but with only a slight increase in the number of cells stained with Leu 2a, 7, 11, and M3 antibodies. This augmenting effect was more prominent in patients receiving two SPG injects that in those with a benign tumor. These results suggest that stimulus with some antigen (cancer antigen in the present study) may be required to induce immuno-augmentation by SPG which has no antigenicity. Interestingly, the above augmenting effects could be seen even in metastatic lymph nodes from advanced cervical cancer patients. SPG was thus revealed to be a potent biological response modifier leading to augmented helper T (Th) cell functions of pelvic lymph nodes in cervical cancer patients, among which an enhanced IL-2/IL-2R system was noted.