Changes in mycelial dry weight and soluble protein amounts and acid phosphatase activities on a mycelial dry weight basis in the mycelia and culture supernatants during the Pi-supplied (P+) and Pi-depleted (P-) cultures of three strains of Pholiota nameko were examined. Mycelial dry weights of the three strains were lower in the P- culture than in the P+ culture. However, soluble protein amounts in the culture supernatants and acid phosphatase activities in the mycelia and culture supernatants of the three strains were higher on a mycelial dry weight basis in the P- culture than in the P+ culture. Total proteins of strains N2 and N4 were analyzed by two-dimensional-PAGE. Comparison of electrophoretograms of the P+ and P- cultures showed that many polypeptides in the two strains were induced and secreted by Pi deficiency, but more than half of them were specific to each strain. Activity staining of acid phosphatase also revealed that two isozymes with the same molecular weights in the three strains were induced and secreted by Pi deficiency. Adaptive mechanisms for Pi deficiency in the three strains were discussed.