Abstract: Lentinan(LTN) was extracted from Lentinus edodes (Berk)Sing with molecularweight of 5×10⁵.The effects of lentinan on cellular immune function were studied in vivo bymeasuring the cellular delayed type hypersensitivity(DTH)to dinitrofluorobenzene (DNFB)incyclophosphamide(Cy)-comprised mice.The effect of lentinan on T lymphocyte proliferation toCon A on splenocytes and T lymphocyte subpopulations on thymocytes and on splenocytes from normalmice were also evaluated.Moreover, the effect of LTN on production of tumor necrosis factor(TNF) from murine peritoneal macrophage was also tested.LTN was administrated at doses of 1,5and 10 mg·kg^-1·d^-1.The following results were observed :LTN administration(×6) augmentedthe T lymphocyts proliferation to Con A in normal mice; LTN restorated the DTH to DNFB impairedby single Cy(200 mg· kg^-1 and 80 mg· kg^-1 ,ip)after using LTN for 8 or 5d;LTN administration(×6)either decreased the nercentage of L3T4⁺(Th),Lyt2⁺(Ts)in thymocytes or increased thepercentage of L3T4⁺,Lyt2⁺ in splenocytes;LTN(×6)administration elicited release of TNF fromMth in the presence of lipoplysaccharide(LPS).These results indicate that the immunomodulatingeffect of LTN mav be relevant to change of T cell subpopulation and increase of TNF production.