Sodium (N-acetyl-N-phenylhydroxylamine beta-d-glucosid)uronate was isolated from the urine of rabbits receiving N-acetyl-N-phenylhydroxylamine. 2. Its chemical structure was confirmed by the correspondence of the infrared spectrum of its tri-O-acetyl methyl ester derivative with the tri-O-acetyl methyl ester derivative of an authentic specimen prepared by the Koenigs-Knorr synthesis.