Ishikawa et al. 1983;Matsumoto 1988;Ohga 1992;.The fruiting process in higher fungi is connected with several biochemical changes. Among others, these relate to levels of laccase, peroxidase, and phenol oxidase, which take part in the metabolism of phenolic compounds and in the degradation of lignin (Eriksson et al. 1990;Hammel et al. 1993;Leonowicz et al. 1999). Phenolic substances are active in the process of building mushroom cell walls (Kitamoto et al. 2000). Phenols are very sensitive to the presence of active forms of oxygen and can be subject to various oxidative processes. Superoxide radicals are also able to initiate these processes, and it is known that autooxidation of diphenols decreases in the presence of superoxide dismutase (SOD) (Misra and Fridovich 1975). During enzymatic oxidation of diphenols, H 2 O 2 is also generated, becoming a good electron acceptor for peroxidase, and it activates enzyme change (Jiang and Miles 1993).The purpose of this article is to report on the changes in phenol oxidases [peroxidase, laccase, and Mn-dependent peroxidase (MnP)] and SOD, which take part in lignin metabolism, and on the level of phenols and free radical during the fruiting process.Two strains of Pleurotus species from the Fungi Collection of Cheongju (FCC) and the Fungi Collection of Lublin (FCL) were used; these were P. ostreatus (Jacq.: Fr.) Kummer (FCC-822) and P. sajor-caju (Fr.) Singer (FCL-215). The fungi were cultivated in polypropylene bags containing 1.5 kg of solid beech sawdust-wheat bran medium (80 : 20 w/w). The bags were incubated for 30 days at 25°C and moved to a conditioned room at 8°-15°C and 90% humidity for about 5-10 days for primordia formation. When the first primordia appeared, the culture bag was opened and moved to an illuminated room (about 500 lx) at 10°-15°C for 10 days for fruit-body growth. Samples were taken from cultures at various stages of development: mycelium before fruiting (Mbf) on the 30th day from inoculation, primordia (P) on the 35th day, small fruit-body (F1) on the 42th day, medium fruit-body (F2) on he 45th day, large mature fruit-body (F3) on the 50th day, and mycelium after fruiting (Maf) on the 60th day. Five liters of 50 mM Abstract Peroxidase and laccase activities increased rapidly up to the formation of primordia and then declined throughout the entire stage of fruiting. In the case of Pleurotus ostreatus, the level of Mn-dependent peroxidase was very low in primordia and fruiting stages but gradually increased with the growth of the fruit-body, whereas no activity was detected in Pleurotus sajor-caju during all growth stages. Superoxide dismutase activity was observed mainly at the fruiting stages. These results show that changes in concentration of lignin-related enzymes are associated with the fruiting process.Key words Fruit-body · Lignin-degrading enzymes · Phenol oxidase · Pleurotus · Superoxide dismutase Fruit-body development of mushrooms generally consists of two stages. One stage is primordia formation, which requires relatively lower temperat...