Background and aims: To assess the effect on irritable bowel syndrome (IBS) of treating ano-rectal problems by applying multiple Barron's bands to prolapsing mucosa and excising haemorrhoids, with or without a low lateral sphincterotomy. Patients and methods: 144 patients with IBS whose ano-rectal abnormalities were treated by a single consultant surgeon. A prospective 'within person' study of consecutive patients referred with ano-rectal problems who also had IBS symptoms according to the Rome criteria. All patients completed structured questionnaires about anal and IBS symptoms before operation and 6-60 months later. The findings were compared with those from patients who had no abdominal pains. Results: The principal IBS symptoms of abdominal pain, abdominal distension, and altered bowel habit all improved significantly after operation. Those with persistent anal problems had more problems with persistent IBS symptoms, but when the anal problems were corrected, the IBS tended to settle. Posterior anal tenderness is present in 80% of IBS patients and is a useful diagnostic sign. Conclusions: This work suggests that in many patients with IBS there is a physical ano-rectal disorder amenable to physical treatment. Patients with IBS should all be proctoscoped carefully, with and without the patient straining, looking for abnormalities. Correcting mucosal prolapse and other anal problems produced an improvement in IBS symptoms in 86% of patients. This suggests that ano-enteric reflexes are a significant factor in irritable bowel syndrome, if not the major cause.