Chemotherapy and/or radiotherapy are believed to further lower the already low cellular immunologic response of cancer patients giving poorer prognosis. A number of Chinese medicinal herbs known as Fuzheng therapy (FZT), in which AM is an active one, are being used to enhance the natural host defence function in cancer patients. Among some fractions of AM polysaccharide extracts, FB was the strongest. In vitro restorative effects of FB in 18 normal healthy individuals and in 9 previously untreated advanced cancer patients are reported. Local graft versus host (GVH) reaction and blastogenic response of lymphocytes in vitro (BRL) were used as test index for T-cell function. GVH reaction nodules with a volume greater than or equal to 50 mm3 were considered as positive GVH reaction. FB 100 micrograms/ml induced a restored reaction in 18 normal donors with an increase in local GVH reaction from 69.6 +/- 20.8 mm3 to 148.9 +/- 40.8 mm3 (P less than 0.001) and in 9 cancer patients with an increase in local GVH reaction from 29.3 +/- 9.5 mm3 to 137.2 +/- 35.8 mm3 (P less than 0.001). The local GVH reaction of the 9 cancer patients went from negative to positive. FB on BRL was detected. 10 micrograms/ml of FB augmented the spontaneous 3H-TdR incorporation in the lymphocyte of 18 normal subjects from 310.2 to 910.9 counts per minute (cpm) and of 9 patients from 248.5 to 642.2 cpm, but the effects were not strong. The effect of single mitogen was not remarkable.(ABSTRACT TRUNCATED AT 250 WORDS)