A chitinolytic bacterium of the genus Pseudomonas, isolated from a pond, was grown in liquid culture. Culture filtrates were subjected to purification procedures. The extracellular material was found to contain chitinase and chitobiase activity. The chitinase activity was isolated from contaminating proteins by ammonium sulfate fractionation, affinity chromatography, and molecular weight exclusion chromatography. Overall purification was found to be three-fold, with a recovery of fourteen percent of the `original activity. Polyacrylamide gel electrophoresis showed the presence of two proteins, both exhibiting chitinase activity.