Abnormal dilation of the colon and rectum can develop from a range of disease processes. When encountered at autopsy, its contribution to death requires assessment and a thorough investigation of its origins. Elimination of known causes elicits a diagnosis of idiopathic megacolon. This entity is uncommonly encountered and presents with similar gross anatomic findings as Hirschsprung disease. Although death is infrequent, it most commonly results from disruption of the bowel wall and subsequent peritonitis. The authors report 2 rare deaths from idiopathic megacolon with retained integrity of the bowel wall. The first was a 9-year-old girl who was administered a laxative and subsequently died the following day. She expressed difficulty passing stool since birth with a marked decline at the age of 7 years. The second case was a 16-year-old adolescent girl with recent diarrhea who collapsed after showering. She, too, had a long history of chronic constipation. Years before death, her rectum and sigmoid colon were found to be dilated on x-ray for an unrelated event, but follow-up was never pursued. Cases such as these require a thorough review of the medical history and exclusion of established conditions, such as infectious, inflammatory, metabolic, and neurogenic origins.