Abstract: SPG₁ and SPG₂ are polysaccharides extracted respectively from fermented cultural mycelium and fermentation fluid of Schizophyllum commune. This paper reports the effect of SPG₁ and SPG₂ on concanavalin A (Con A) induced proliferation of lymphocyte from C₅₇BL/6J mice in vitro. SPG₁ (10, 25, 50 and 100 μg/ml) and SPG₂ (10, 50 and 100μg/ml) was found to significantly increase lymphocyte proliferation. In addition, SPG₁ (10, 25, 50 and 75μg/ml) antagonized the suppressive effect of hydrocortisone on proliferation of mouse spleen cells, while SPG₂ did not. In vivo, at the dose of 2.5 and 5.0 mg/kg ip for 9 days, SPG₁ and SPG₂ remarkably enhanced the delayed-type hypersensitivity to 2, 4-dinitrochlorobenzene (DNCB) in mice. SPG₁ (1.25, 2.5 and 5.0mg/kg, ip for 1 day) and SPG₂ (2.5 and 5.0 mg/kg, ip for 1 day) promoted the plaque forming cell(PFC) response to sheep red blood cells (SRBC) in mice. The effects of SPG₁ and SPG₂ on immune function were studied in aged immunodeficient mice. SPG₁ (10 and 25 μg/ml) and SPG₂ (25 μg/ml) was found to enhance the Con A induced lymphocyte proliferation in 14 months aged mice. At the dose of 2.5 mg/kg, SPG₁ and SPG₂ produced respectively 162.1 and 136.0% increase in PFC response in 14 months aged mice.