Octyl glucoside stimulated peroxidase formation in Phanerochaete chrysosporium ME-446 cultivated in cellulose-based media. Addition of 0.1% of the nonionic surfactant resulted in a ninefold (143 U/L) and sixfold (119 U/L) increase in LiP formation under conditions of N limitation and N excess, respectively. Octyl glucoside also stimulated MnP formation, but to a lesser extent than observed with LiP. The cellobiose-oxidizing enzymes (cellobiose dehydrogenase and cellobiose:quinone oxidoreductase) were stimulated by octyl glucoside when used at a concentration of up to 0.05%, but higher concentrations gave values similar to those for the controls. Little proteolytic activity was detected in the presence of the surfactant. In general, activities of the enzymes studied were of the same order as those seen using Tween-80. In contrast with Tween-80, octyl glucoside markedly inhibited [C-14]DHP mineralization. Attempts to account for the observed inhibition of synthetic lignin degradation by P. chrysosporium in the presence of octyl glucoside are discussed.