The aim of this study was to compare the chemical composition and susceptibility to enzymatic hydrolytic cleavage of several polysaccharides synthesized by glucosyltransferases obtained from oral streptococci. Glucosyltransferase enzymes were obtained from cultures of Streptococcus mutatis, strains HS-6 and AHT (antigen a), FA-1 (antigen b), Ingbritt and GS-5 (antigen c) and OMZ-176 (antigen d), and from Streptococcus sanguis, strain 804. These enzymes were partially purified by absorbing the culture supernatant fluid of the respective strains onto hydroxylapatite gel and eluting batchwise from the gel. Polysaccharides were prepared by incubating the eluted enzymes in the presence of sucrose, followed by precipitation with alcohol (1:1 v/v), washing, dialysis and finally lyophilization. Analyses indicated the polysaccharides were essentially homopolymers of glucose with 2–7% moisture, 85–98% total carbohydrate, 78–98% glucose, 0.9–2.6% fructose and about 0.5% nitrogen. Suspensions of each of the glucans were treated with 3 commercial preparations of dextranase or 3 commercially available amyloglucosidases. Amyloglucosidases were largely ineffective in hydrolyzing these bacterial glucans. The dextranase preparations hydrolized the various glucans at significantly different rates. The rate and degree of cleavage appears to be related to the antigenic grouping of the strain. The relative resistance of some glucans to degredation under these conditions may explain the ineffectiveness of the dextranase mouthwash in human clinical trials.