Abstract: The tolerance of 46 wood-decomposing Hymenomycetes to 23 phenolic and rehted aromatic compounds was investigated by adding the compoudns to Hagem agar after autoclaving and cooling it to 70-80°C, and measuring the radial growth on these substrates after 8-10 days (Table 1). Considerable differences in tolerance were found between the species. The most tolerant were brown-rot fungi, white-rot fungi being on the average more sensitive. When natural substrates of these fungi were treated with FeCl3 solution to reversal the presence of phenols, a positive reaction was generally obtained with the brown-rot, but not with the white-rot fungi. The results suggest that phenolic compounds may be important in the ecology of wood-decomposing fungi, e.g. in connection with the drying of wood.