Abstract The results of treatment of 188 consecutive new patients with a primary diagnosis of fissure-in-ano presenting to the Outpatient Department of St Mark's Hospital are reviewed. One-third underwent operation as the primary treatment and were not studied further. Of the remaining patients who underwent non-operative treatment only, one-half were initially cured. Follow-up at 4 years showed that this cure was maintained in half of these-cases, suggesting that there is aplace for treatment with a dilator in the correctly selected case. The presence of a sentinel skin tag or a fibrous anal polyp is shown to have a statistically significant association with operative treatment. The use of a paediatric sigmoidoscope ro diagnose a fibrous anal polyp is recommended.