AIM Anal fissure is associated with hypertonia of the internal anal sphincter and pain. Lateral internal sphincterotomy, the most common treatment, may cause permanent injury to the anal sphincter, which can lead to fecal incontinence. The aim of this study was to evaluate the effectiveness of topical glyceryl trinitrate (GTN) ointment in the treatment of anal fissure. METHODS Twenty-four patients (12 males and 12 females, mean age 45 years) with anal fissure received 0.4% GTN gel twice a day for a minimum of six weeks. All patients were followed at regular intervals of 2, 6, 12 weeks to assess symptom outcome, rate of healing, adverse effects and recurrence rate. RESULTS The symptomatology was significantly improved already from the second week of treatment in 18 patients (75%). Thirteen patients (54%) healed after six weeks, and 14 (58%) after 12 weeks, while three patients (13%) partially healed but asymptomatic. Fecal incontinence was absent. In two patients (8%) treatment was interrupted because of severe headaches. At the end of the treatment, only three patients (13%) underwent lateral sphincterotomy. CONCLUSIONS Topical application of GTN ointment heals anal fissures and represents an alternative to the traditional first-line treatment of surgical sphincterotomy.