Although Hirschsprung's disease is diagnosed most commonly during infancy and childhood, some cases are seen in adults, when clinical features are usually similar to those described in younger patients. We report a case whose unusual clinical presentation led to an initial diagnosis and subsequent treatment of colonic Crohn's disease. The correct diagnosis was made only after motility measurements suggested the possibility of adult Hirschsprung's disease and prompted the histological examination of the myoenteric plexus, which led to the establishment of the correct diagnosis.