Abstract: Plant indican (indoxyl-β-glucoside) is identified as the principal constituent in the extract of Ta-Tsing-Yeh (大青叶), leaves of Polygonum tinctoria Lour., a kind of medicinal herb used for centuries. A preliminary test recently made in this laboratory has disclosed that indican possesses some anti-viral activity. Oral doses of 150-200 mg of plant indican were given to human subjects, including normal man and hepatitis patients, as well as dogs and rabbits. The 24-hour urine was collected and treated with Dalgiesh's deactive carbon method, then paper chromatographed and the metabolites identified. Beside unchanged plant indican, urinary indican, and indoxyl-d-glucuronic acid which were supposed to be the main metabolites, were found in all samples of urine. Furthermore, some strongly polar unknown compounds were also found which we presumed to be x-hydroxy indoxyl conjugates. Anthranilic acid and O-aminobenzoylglycine were detected as transformation products in the urine of the rabbit only. The metabolic products found in the urine samples of both normal persons and patients of hepatitis revealed no qualitative difference. The results indicates that the bio transformation of plant indican is in accord with the normal route of physiological detoxification. No attempt on quatitative determinations was made except some simple comparisons. One more point worthy of mentioning is that, according to Tollens and Kauffmann simple indole (200 mg) taken by human beings is verted to urinary indican only and no indixyl-d-glucuronic acid formed.