This paper describes mass spectrometric studies on the metabolism of 4,5-diphenyl-2-bis-(2-hydroxyethyl)-amino-oxazole (ditazole, Ageroplas) in man. The metabolites were identified after cleavage of conjugates, extraction and derivatisation in urine of healthy volunteers orally administered with 400 mg of ditazole each. Besides the unchanged ditazole the following 7 metabolites could be detected: N-desalkyl and N,N-bisdesalkyl ditazole, hydroxy ditazole, N-desalkyl-hydroxy and N,N-bisdesalkyl-hydroxy ditazole as well as benzil and hydroxy benzil. Therefore, two main metabolic pathways, the aromatic hydroxylation and the N-desalkylation, can be postulated. Ditazole and its metabolites (with the exception of benzil) are excreted in urine partly in a conjugated form.