A specific acid-stable urinary substance has been isolated in a crystalline state by using cation (Diaion SK-1) (eluant: 2 [image] HC1) and anion exchanger resins (Dowex 1) (eluant: 0.1 [image] HC1), cellulose column chromatography (eluant: a butanol-acetic acid water mixture (25:6:25)), charcoal treatment, precipitation as Ag salt, hydrolysis with H2S, and crystallization from 50% ethanol. This substance contained 43.4% C, 6.7% H(no N value is presented), and showed m.p. at 232 oC(brown coloration). An infrared spectrum is presented.