Abstract The identification of 4-hydroxyphenacetylurea and 3-methoxy-4-hydroxy-phenacetylurea in the urine of rabbits fed phenacetylurea is reported together with that of unchanged phenacetylurea. In addition to these metabolites, hydrolyzed metabolites, phenaceturic acid, and phenylacetic acid were also demonstrated to be excreted into the urine. However, unlike some drugs that possess an amide group in the molecule, the excretion of phenacetylurea N-glucuronide could not be recognized. It is considered from the above results that the metabolic fate of phenacetylurea consists of two different pathways: one is hydrolysis of the ureide group, and the other is successive hydroxylation and methylation of the benzene nucleus. The methyl acetyl derivative of phenacetylurea N-glucuronide was synthesized by acylation of methyl 1-deoxy-1-thioureido-2,3,4-tri-o-acetyl-β- d-glucopyranosiduronate with phenylacetylchloride, and subsequent desulfurization with silver nitrate. 4-Hydroxyphenacetylurea and 3-methoxy-4-hydroxyphenacetylurea were synthesized by condensation of the corresponding acid esters with urea.