The induction of Penicillium verruculosum β-glucosidase by different carbon sources was investigated using by either enzyme activity assay or immunoblot analysis. The activity of extracellular enzyme was maximum with cellobiose octaacetate (COA), followed by mannitol, maltose, laminarin and cellobiose. Regardless of carbon sources, cellular β-glucosidase occurred 48 h earlier compared with extracellular enzyme. The biosynthesis and secretion of enzyme on COA and laminarin occurred 24 or 48 h later than did on cellobiose and maltose. Glucose repressed enzyme synthesis while maltose induced enzyme biosynthesis efficiently.