PURPOSE: Unlike classic Hirschsprung's disease, short-segment and ultrashort-segment varieties are usually found to be latent and milder. Ultrashort-segment Hirschsprung's disease may present as intractable chronic constipation in children over one year of age, adolescents, and adults. Anorectal myectomy has been shown in many instances to provide effective long-term treatment for certain patients with ultrashort-segment Hirschsprung's disease. Histologically, the affected segment in Hirschsprung's disease has been shown to have increased cholinergic nerves, lack of nitric oxide synthase-containing neuronal elements, and show moderate to severe loss of myenteric neurons. METHODS: Here, we report three cases that showed clinical and manometric evidence of ultra-short-segment Hirschsprung's disease. Two of the three patients responded well to myectomy. RESULTS: Detailed histologic and immunohistochemical evaluation of the internal anal sphincter and a comparison with three normal controls revealed absence of nitric oxide synthase-containing neurons in both cases that responded well to surgery and continued presence of these neurons in the patient who did not respond. A review of the current literature on various treatment modalities is included. CONCLUSIONS: Anorectal myectomy provides long-term relief of this chronic problem in a subgroup of patients with ultrashort-segment Hirschsprung's disease who lack nitrinergic neurons at the internal anal sphincter.