This study was carried out to elucidate the immunomodulating activity of protein bound polysac charide extracted from Ganoderma lucidum(PSG). Macrophage drived reactive radicals were known as an effector for antimicrobial and anticancer functions. The promising immune response molecule, reactive oxygen intermediates(ROIs), was determined in TIB 71 cells with PSG at various experimental conditions. Treatment with 0.5mg PSG significantly increased the production of ROIs, superoxide anion as well as hydrogen peroxide, from TIB 71 cells(p<0.001). Under the same concentration, con siderable results were obtained from 24 hour cultivation with 106 cells at 5% CO2 incubator. The cells were trigged with PMA(5.3 M) after primed BCG(100 M) or IFN (100U) alone could not induce the production of ROIs, but it had a significant potentiating effect on ROIs secretion when the cells were treated with PSG.