In order to investigate the immunomodulatory mechanism of Ganoderma lucidum, the effects of protein-bound polysacchride of Ganoderma lucidum on the proliferation and cytokine gene expression of mouse peritoneal macrophages was studied. In the macrophage proliferation assay using the BrdU labeling reagent, the GLA component extracted from Ganoderma lucidum or GLB from the bud of Ganoderma lucidum were added to the medium at the concentration of 0 to 256ug/ml. DNA synthesis of the macrophage was increased at 16ug/ml of GLA and 64ug/ml of GLB, respectively. In the reverse transcription polymerase chain reaction(RT-PCR), the cytokine(TNF, IL-1, and IL-12) gene and $eta$-actin expression were also analyzed. 20$mu extrm{g}$/ml of either GLA or GLB increased TNF and IL-1 expression of the macrophages.