Sorbitol (d-glucitol) metabolism in Aerobacter aerogenes PRL-R3 is shown to proceed via the pathway: sorbitol --> sorbitol 6-phosphate --> d-fructose 6-phosphate. Sorbitol phosphorylation is mediated by a phosphoenolpyruvate (PEP):sorbitol 6-phosphotransferase system, and sorbitol 6-phosphate oxidation by a pyridine-nucleotide-linked dehydrogenase. Mutants deficient in sorbitol 6-phosphate dehydrogenase or a component (enzyme I) of the phosphotransferase system did not grow on sorbitol, whereas revertants which had regained these enzymatic activities grew normally. Extracts of the enzyme I-deficient mutant failed to catalyze the phosphorylation of sorbitol in the presence of PEP, and adenosine 5'-triphosphate could not replace the PEP requirement for sorbitol phosphorylation in extracts of the wild-type strain.