2-Methyl-3-o-tolyl-4 (3H)-quinazolinone (MTQ) was orally administered to human, and its urinary metabolites were examined. Two kinds of metabolite were isolated from the urine, and one of them was assumed to be 2-nitrobenzo-o-toluidide. On the other hand, the same compound as this metabolite was obtained by chemical oxidation of MTQ with hydrogen peroxide in glacial acetic acid. And the chemical structure of this oxidation product of MTQ was established as 2-nitrobenzo-o-toluidide. Therefore, one of the metabolites of MTQ, which were isolated from human urine by the authors, was confirmed to be 2-nitrobenzo-o-toluidide.