Crude enzyme solution prepared from the culture filtrate of Aspergillus nidulans FGSC 159 in CMC minimal liquid medium was fractionated through a three-step procedure including chromatography on Sephadex G-150, DEAE-Sephadex A-50 and Sephadex G-200. Three β-glucosidase components, P-I-Ia, P-II-Ia and P-II-Ib, were prepared. All the fractions had their highest activities at pH 6.0. Optimum temperatures were 55℃ for P-I-Ia, P-II-Ia and 60℃ for P-II-Ib, respectively. P-II-Ia was a little more thermostable than the other two components. The substrates specificities for these β-glucosidase preparations were investigated. These enzymes showed specificities to cellooligosaccharides and sugar derivatives with β-glucosidic linkage such as cellobiose, cellotriose, cellotetraose, cellopentaose, sophorose, PNPG and salicin. All three fractions not only hydrolyzed substrates to remove glucosyl residues one by one from non-reducing end but also transferred the glucosyl residues to other acceptor molecules. But P-I-Ia showed some different mode of action from the other two fractions. It did not accumulate transglucosylated products in detectable amounts, when reacted with cellooligosaccharides.