A novel kind of dextranase which is different from the so-far reported dextranases [α-1,6-glucan 6-glucanohydrolase, EC 3.2.1.11] was purified 44-fold from the culture supernatant of a soil bacterium (Achromobacter sp.). This dextranase liberates isomaltose from dextrans in an exo-lytic fashion. During digestion of dextrans the decree of polymerization of the reaction products remained 2. Paper chromatograms of digests of dextran showed that the only product was isomaltose. A high-molecular residual substance (limit dextrandextrin), resistant to this enzyme but susceptible to Penicillium luteum dextranase (endo-type) was recovered after exhaustive digestion of macromolecular dextran by the enzyme. The dextranase split panose into isomaltose and glucose, and isomaltotriitol into isomaltose and sorbitol.