The species concept in Pholiota, stirp Adiposa Smith and Hesler, has been investigated by applying electrophoretic techniques to isolates that have previously been examined for their morphology and mutual mating compatibility. Crude protein extracts of soluble proteins from mycelium grown in liquid shake culture were used to obtain general protein patterns and zyrnograms of esterases, (alphanaphthylamidases), phenoloxidases (laccases and tyrosinases), and peroxidases on polyacrylamide gels. Harvesting of different isolates for protein extraction was carried out at comparable stages of development using dry weight determinations and respiration studies as criteria. Peroxidase and phenoloxidase zyrnograms showed wide areas of activity and no distinct banding patterns were attained. Esterase zymograms displayed characteristics that made it possible to arrange the studied isolates in separate groups, but this classification did not completely follow results from the previous work. The chemotaxonomic approach to the species complex of P. aurivella (Fr.) and P. limonella (Pk.) Sacc. showed that the species are closely related and cannot clearly be separated in this way. / Master of Science