Dihydrocitrinone, 3,4‐dihydro‐6,8‐dihydroxy‐3,4,5‐trimethyiisocoumarin‐7‐carboxylic acid, was isolated and identified as a urinary metabolite after oral administration of citrinin to rats. Male and female Osborne‐Mendel rats received 30 mg citrinin/kg body weight by oral intubation. The metabolite dihydrocitrinone was present in urine collected at 0–2, 2–4, 4–6, 6–8, and 8–24 h after treatment. Only unchanged citrinin was found in blood collected 24 h after administration of the compound. The metabolite had a blue fluorescence and the same Rfon thin‐layer chromatography, the same retention time on reverse‐phase high‐pressure liquid chromatography, and the same mass spectrum as an authentic sample of dihydrocitrinone.