Polyglycols increased lignin peroxidase activity in shaken cultures of Phanerochaete chrysosporium even when they were added to an old fungus (5 or 10 d after inoculation). The effects depended on the polyglycol mol wts (10(2)-10(6) Daltons) as well as on the backbone structure (i.e., poly[ethylene glycol], poly[butylene glycol], poly[propylene glycol]) and terminal groups (i.e., poly[ethylene glycol], poly[ethylene glycol] methyl ether, poly[ethylene glycol] dimethyl ether). The residual quantity of polyglycol in the biomass and in the culture filtrate also varied among different polyglycols. The polyglycols act after being adsorbed to the cell membrane exaggerating the asymmetry of the membrane environment. In old fungus, the incompatibility of polyglycols and glycans decreases the adsorption and the effect of high mol wt polyglycols.