The effects of various factors on the biosynthesis of extracellular laccase (EC 1.14.18.1) by the basidiomycete Coriolus hirsutus (Wulf.: Fr.) Quel. no. 072 during submerged cultivation were examined. Optimal parameters for cultivation in a fermenter of 10 l were determined: temperature, 28 degrees C; stirrer rotation speed, 160 rpm; and the inoculum volume, 15% of the working volume of the fermenter. The filtrate contained peroxidase, laccase, and phenol oxidase activities and displayed a high thermal stability.