Hirschsprung's disease associated with colonic atresia is rare. A boy with colonic atresia at the hepatic flexure who had a colostomy in the neonatal period suffered from severe constipation after definitive colocolostomy. Hirschsprung's disease was diagnosed with anorectal manometry and rectal mucosal biopsy, and a Duhamel-Ikeda's pull-through procedure was performed. Aganglionosis of the entire distal colon was seen, and intrauterine torsion of the dilated proximal colon followed by necrosis and absorption was suspected as the cause of colonic atresia. Colonic atresia should be generally screened for Hirschsprung's disease with a rectal biopsy. J