The glucose-6-phosphate and 6-phosphogluconate dehydrogenases i. e. enzymes of dissimilatory hexulose phosphate cycle, were isolated from the cells of the facultative methylotrophic bacterium Pseudomonas oleovorans. The purification procedure included protein fractionation by ammonium sulfate, gel-filtration through Sephacryl S-200 and chromatography on DEAE Bio-Gel A and phosphocellulose, resulting in a 400-fold purification of the enzyme. During analytical disc-electrophoresis in polyacrylamide gel the glucose-6-phosphate dehydrogenase preparation produced a single band; 6-phosphogluconate dehydrogenase was found to contain small contaminations. The molecular weights of the dehydrogenases are 100000 and 110000, respectively. Both enzymes have two subunits. The Km values for glucose-6-phosphate dehydrogenase are 65 mkM for glucose-6-phosphate and 28 mkM for NADP; those for 6-phosphogluconate dehydrogenase are 152 mkM for 6-phosphogluconate and 55 mkM for NADP. Nucleotides are found to be the most active inhibitors of glucose-6-phosphate dehydrogenase. 6-Phosphogluconate dehydrogenase is inhibited by ribose-5-phosphate and fructose-1,6-diphosphate.