We report a case of enteric mucocele formation in a 4-year-old boy after endorectal pull-through correction for Hirschsprung's disease with proximal intestinal neuronal dysplasia. On 17 April 1997, when the patient was 2 years old, a loop ileostomy was performed after an ineffective endorectal pull-through operation involving the right colon. Because of frequent prolapse of the stoma, when the child was two-and-a-half years old an end ileostomy was made by a resection of the distal ileotoma and redundant terminal ileum. When he was 4 years old, he was readmitted because of ileus, peritonitis, and a huge abdominal mass. Complete atresia of the colon at the level of pelvic reflection with proximal enteric mucocele formation was noted at laparotomy. He made an uneventful recovery after resection of the mucocele. This is the first reported case of such a complication after an endorectal pull-through operation. The possible causes and techniques for the prevention of this complication are discussed.