The effect of fungal and yeast glucan on different immune functions in mice was examined and compared. The simultaneous administration of glucan and a sensitizing dose of DNFB on the different sites significantly stimulated delayed-type hypersensitivity (DTH) response only when using fungal glucan. Both glucans tested, when administered before sensitization, significantly increased DTH response, but with a significantly higher level at the beginning of the investigation (on day 7) when using fungal glucan. The increase in phagocytic activity by the blood leucocytes started in the 1st week after fungal-glucan treatment, and in the 2nd week after yeast-glucan treatment, and took longer after administration of fungal glucan. The values of the phagocytic-activity index were significantly influenced only after fungal-glucan injection. The results of the study indicate that fungal glucan isolated from Pleurotus ostreatus could be a prospective immunomodulating substance.