A 15-day course of Naloxone treatment was given to a patient with intestinal pseudoobstruction who had previously undergone subtotal colectomy with terminal ileostomy for invalidating constipation. The effects of the drug were assessed according to symptoms, by recording the myoelectric activity of the stomach, and by measuring gastric emptying of a radiolabeled solid-liquid meal and the intestinal transit time of radiopaque markers. All tests were performed 1) at baseline; 2) after 2 wk with Naloxone 1.6 mg subcutaneous per day; and 3) after 8 days of placebo. Results showed that before treatment gastric emptying of solids was delayed, emptying of liquids was normal, myoelectric activity of the stomach was normal, small intestinal transit time of radiopaque markers was considerably increased while ileal output was markedly decreased. After Naloxone, gastric emptying of solids was markedly accelerated, emptying of liquids remained normal, gastric electrical spiking activity increased, small intestinal transit time strikingly decreased, and ileal output increased. After placebo, a tendency to return to pretreatment values was observed. This observation suggests that Naloxone may be helpful in the treatment of some patients with intestinal pseudoobstruction.