Of 111 consecutive patients treated by partial internal sphincterotomy for a haemorrhoidal disease in the course of a prospective study, 101 could be re-examined between 24 and 36 months after operation. There were no major complications but 11 patients had some significant complaints at some time after operation. There were six recurrences, five of which could be attributed to inadequate sphincterotomy. One patient had an excessive sphincterotomy which led to difficulties with continence of fluid stools. One patient developed a peri-anal abscess two years after partial sphincterotomy and four patients with marked soiling will require surgical correction of the posterior gutter. The gutter is due to secondary epithelialisation after open sphincterotomy in the posterior midline. The recommended technique entails the division of the internal sphincter up to a few millimeters above the dentate line and reconstruction of the anal mucosa with a continuous absorbable suture. 'Landscaping' by partial resections of the prolapsed haemorrhoids is recommended to avoid sclerotic tags. Submucosal sphincterotomy should be considered by the very experienced only and then provided that the anal mucosa shows little scarring.