Two cases of vincristine-induced paralytic ileus are described, with therapeutic correlation. Both patients had a roentgenographic picture of paralytic ileus showing fecal mass in the ascending colon and dilated bowel loops. One patient was successfully treated with glycerin and saline enema through a fiberoptic colonoscope placed in the ascending colon. The second patient was successfully treated with intravenous prostaglandin F2 alpha (PGF2 alpha). Enema through a fiberoptic colonoscope or the intravenous administration of PGF2 alpha may, therefore, prove useful in the treatment of vincristine-induced gastrointestinal toxicity.