The effect of adding some activators of ligninolytic enzyme production, Tween 80, veratryl alcohol and manganese (IV) oxide, to semi-solid-state cultures of Phanerochaete chrysosporium BKM-F-1767 (ATCC 24725) was studied. As carrier, cubes of polyurethane foam were employed. Supplementing the cultures with Tween 80, a maximum manganese-dependent peroxidase (MnP) activity of 350 U/l was achieved. This value was about 3-fold higher than that obtained in the control cultures (without Tween 80). When not only Tween 80 but also veratryl alcohol or manganese (IV) oxide were incorporated into the culture medium, the effect was greater and led to MnP activities of about 600 and 1100 U/l with alcohol or oxide, respectively. These activities were notably higher than those obtained in the control cultures (about 3-fold and 7-fold, respectively). The decolourisation of the dye Poly R-478 by the above-mentioned cultures was investigated. The percentage of biological decolourisation reached at the end of all the cultivations was higher than 95%.