Many different materials have been tested for beta-glucosidases immobilization. Such materials, however, often show a poor activity related to a low surface area of the support or even enzyme hindrance caused by entrapment inside porous matrix. In this context, the use of nanosized zeolites as enzymes support is quite new and may be an interesting alternative. The present work evaluates the immobilization of beta-glucosidases in nanosized silicalites by covalent coupling. The new biocatalyst was able to convert 100% of cellobiose into glucose in 18 h at 50 degrees C and pH 5, retaining 85% of its activity after five cycles of reuse. A detailed investigation of the published literature indicates that, apparently, this is the first work concerning the immobilization of beta-glucosidases on nanosized zeolites ever reported.