The beta-glucosidases (beta-D-glucoside glucohydrolase, EC 3.2.1.21) hydrolyze glycosidic bonds of alkyl-, amino-, or aryl-beta-D-glucosides, cyanogenic glucosides, disaccharides and short oligosaccharides and can also catalyze the synthesis of glycosyl-bonds between different molecules via transglycosylation. Due to their ubiquitous phylogenetic distribution, substrate diversity and ability to both hydrolyze and synthesize glycosidic bonds, the catalysis and regulation of beta-glucosidases have been extensively studied. Many beta-glucosidases are inhibited by the reaction product glucose, and reduced catalytic activity may limit the biotechnological and industrial applications of these enzymes and this has stimulated the search for beta-glucosidases that maintain their activity at high glucose concentrations. Studies of many glucose tolerant enzymes have been reported and due to the ongoing interest in these enzymes, here it has been reviewed this accumulated body of knowledge which provides valuable insights as to the kinetics, structure, regulation and evolution of glucose tolerant and glucose stimulated beta-glucosidases.