At an abdominal operation 20 mg of 17B-oestradiol was injected into an isolated intestinal loop with the arterial blood supply preserved. Huge amounts of conjugated oestrone were found in extracts of the intestinal wall and of the effluent venous blood, respectively. The conjugated oestrone was identified as oestrone glucosiduronate. Very little if any oestrone sulphate was found. Preliminary evidence suggesting the intestinal formation of 170-oestradiol-3-glucosiduronate (or 3,17-diglucosiduronate) was also obtained.