For lignocellulosic biomass hydrolysis to be a cost effective process for producing fuel ethanol, the efficiency of the enzyme mix used in the saccharification step needs to be improved.  At least three types of cellulase activities, working synergistically, are necessary for the efficient degradation of cellulose.  These enzymes include exoglucanases, which proceed processively along the cellulose chain, releasing cellobiose; endoglucanases which cleave the cellulose polymer anywhere along the chain, creating new chain ends; and beta-glucosidases which convert cellobiose and other oligosaccharides to glucose. In addition to creating a fermentable product, beta-glucosidase also relieves product inhibition for the exo and endoglucanases from cellobiose.  While it is well known that small amounts of beta-glucosidase are necessary for efficient cellulose hydrolysis, the type and amount of beta-glucosidase can have a profound effect on the extent of the overall hydrolysis.  This talk will focus on the impact of various beta-glucosidases on the specific performance of T. reesei cellulase mixtures in the context of lignocellulosic biomass hydrolysis. Kinetic studies of several beta-glucosidases on small molecule substrates will also be discussed.