The effect of carbon source on the production of a single extracellular β-glucosidase by Acremonium persicinum was investigated using fast protein liquid chromatography. The enzyme was detected in the medium during growth of the fungus on a wide range of β-glucans, particularly those containing a high proportion of (1→6)-β-linkages. While growth of A. persicinum on gentibiose, cellobiose and laminari-oligosaccharides moderately increased β-glucosidase production, growth on sophorose provoked 10-fold greater levels of this enzyme in the culture medium. Levels of the β-glucosidase were minimal in the presence of even low concentrations of glucose, sucrose, fructose or galactose. The results are consistent with the extracellular A. persicinum β-glucosidase being an inducible enzyme, subject to carbon source control by readily metabolizable sugars, with sophorose possibly directly inducing its synthesis.