Anal sphincter spasm is a common finding in patients with anal fissure disease. It is postulated that spasm impedes mucosal blood flow and impairs healing. Topical nitroglycerin (NTG), a nitric oxide donor compound, has been shown to cause relaxation of the anal sphincter and may have treatment efficacy in the management of anal fissure. The purpose of this study was to assess the usefulness of NTG for anal fissure. We performed a retrospective review of patients with anal fissure treated with various concentrations of topical NTG ointments over an 18-month period ending July 1997. Of the 81 patients studied, 44 (54%) were male. There were 42 acute and 39 chronic fissures. NTG preparations included 1 per cent isosorbide (n = 37), 0.2 per cent NTG (n = 38), and 0.5 per cent NTG (n = 6). Healing with NTG therapy occurred in 29 acute (69%) and 21 chronic fissure (54%) patients. There was no difference in the incidence of healing of acute or chronic fissure between the various NTG treatment preparation groups. When acute and chronic fissure therapy was subdivided by time of NTG treatment (immediate versus post-conservative therapy failure (PCF)), 14 (74%) of acute PCF and 5 (42%) of chronic PCF patients healed. We conclude that no single formula was superior. When patients were subdivided into a PCF group, NTG therapy demonstrated a significant salvage rate, thus avoiding surgery.