A 19-year-old woman was admitted to our clinic because of abdominal distention and severe constipation from infancy. Barium enema revealed a grossly dilated descending colon in the right of the abdomen. At laparotomy, with diagnosis of Hirschsprung's disease associated with non-obstructing intestinal malrotation (non-rotation type), division of the adhesion between caecum and duodenum, and modified Duhamel's procedure were performed. The association of Hirschsprung's disease and intestinal malrotation is rare, and to date only 20 infantile case have been reported. The present case would be the first adult case.