Radionuclide peritoneoscintigraphy has been used prior to chromic phosphate P-32 (P-32CP) intraperitoneal therapy to assure proper placement of the catheter in the peritoneal cavity, to exclude loculation, and to predict inadequate distribution of P-32CP. This is a case report of the detection of a peritoneal catheter improperly placed into the bowel lumen by pretherapy radionuclide peritoneoscintigraphy, and this case demonstrates the distinguishing characteristics of the radiocolloid distribution secondary to an intraluminal injection relative to an intraperitoneal injection.