Chronic anal fissure is an extremely common problem of the anorectum. It is often confused with symptomatic hemorrhoids and is frequently missed by the examining physician. Symptoms are most commonly pain and bleeding after defecation. A simple office procedure involving partial lateral internal sphincterotomy with or without excision of a sentinel tag has been used over the past five years with extremely satisfactory results. This procedure was used upon 86 patients. Anatomic and symptomatic relief was obtained in 96.4 per cent of the patients. Due to diagnostic related groups and attempts at cutting medical costs by avoiding hospitalization, sphincterotomy performed as an office procedure is the method of choice for treating chronic anal fissures unresponsive to medical management. Hospitalization is rarely required.