The hydrolytic enzyme trehalase was demonstrated in mycelial extracts of Schizophyllum commune cultured on either glucose or trehalose as sole source of carbon and energy. The enzyme was also detected in culture-filtrates of trehalose-grown cells. The intracellular forms of trehalase from glucose- and trehalose-cultures were similar in their response to dialysis and heat treatment as well as pH optimum, affinity constant for trehalose and resistance to a variety of sugar alcohols.