The production of extracellular peroxidase by twenty-five strains of Coprinus species was investigated for the purpose of its application to the removal of phenolic and other aromatic compounds from industrial waste streams. After initial screening experiments, the production of peroxidase by three superior strains of C cinererus UAMH 4103, UAMH 7907 and IFO 30116 was monitored over a 15-day period. Peroxidase activity was detected after 3 days of growth and had reached itspeak another 6 days later. The peroxidase activity appeared to increase with a corresponding depletion of glucose concentration and rapidly declined immediately after the exhaustion of glucose. The effectiveness of the cultivated C. cinereus peroxidase (CIP) for the removal of aqueous phenol was evaluated in the presence and in the absence of additives including polyethylene glycol (PEG) and chitosan, and compared with those of purified horseradish peroxidase (HRP) and Arthromyces ramosus peroxidase (ARP). The addition of PEG and chitosan enhanced the efficiency of phenol transformation catalyzed by CIP by the factor of 1.5 and 1.3, respectively. Although the efficiency of phenol transformation was higher with CIP than those with purified HRP and ARP in the absence of addtives, its superiority diminished in the presence of PEG. This suggests that the by-products of fungal culture in the crude CIP solution, presumably polycarbohydrates and proteins, have protective effects on the enzyme against inactivation during catalytic transformation of phenol, and the addition of PEG provides small effects on further protection.