Submerged cultures of four Pleurotus species, a popular mushroom cultivated in Egypt, was used for production of bio­active protein-bound polysaccharides. The maximum concentration of mycelia! biomass approximated 10 g1' with 2.76 g/1'¹ protein in Pleurotus &tea after 14 days incubation in shake flask culture. The exopolysaccharide (EPS) production after the same incubation period was higher in P. sajor-caju and P. Aorida (1.4 g/r¹) than P. ostreatus and P. erengii (0.8 g/1^-1). The main components of the isolated polysaccharides were glucans as shown by the NMR spectra. The electrophoretic pattern indicates that the separated polysaccharides are bound to proteins and the molecular weight ranges from 10 to 200 KD. The polysaccharide showed a notable proliferation activity for peripheral blood mononudear cells (PBMC).