Cell extracts of the filamentous fungus Cunninghamella elegans contain epoxide hydrolase (EC 3.3.2.3), glutathione S-transferase (EC 2.5.1.18) and UDP-glucuronosyltransferase (EC 2.4.1.17) activities. Epoxide hydrolase activity was determined with p-nitrostyrene oxide as substrate and was shown to be associated with the 100 000 g pellet obtained from disrupted mycelia. Glutathione S-transferase activity was demonstrated with 1-chloro-2,4-dinitrobenzene and p-nitrobenzyl chloride as substrates. The presence of two or more glutathione S-transferase activities was indicated by different activity ratios for the two substrates in different extracts, and by distinct thermal denaturation curves. UDP-glucuronosyltransferase activity with 3-hydroxybenzo[a]pyrene as substrate was found only with the non-sedimentable fraction prepared from ruptured mycelia.