Background In patients with faecal incontinence in whom conservative treatment fails, options are limited for those with a functionally deficient but morphologically intact sphincter. We investigated the effect of sacral nerve stimulation on continence and quality of life. Methods In this multicentre prospective trial, 37 patients underwent a test stimulation period, followed by implantation of a neurostimulator for chronic stimulation in 34. Effect on continence was assessed by daily bowel-habit diaries over a 3-week period and on quality of life by the disease-specific American Society of Colon and Rectal Surgeons (ASCRS) questionnaire and the standard short form health survey questionnaire (SF-36). Every patient served as his or her own control. Findings Frequency of incontinent episodes per week fell (mean 16·4 vs 3·1 and 2·0 at 12 and 24 months; p<0·0001) for both urge and passive incontinence during median follow-up of 23·9 months. Mean number of days per week with incontinent episodes also declined (4·5 vs 1·4 and 1·2 at 12 and 24 months, p<0·0001), as did staining (5·6 vs 2·4 at 12 months; p<0·0001) and pad use (5·9 vs 3·7 at 12 months; p<0·0001). Ability to postpone defecation was enhanced (at 12 months, p<0·0001), and ability to completely empty the bowel was slightly raised during follow-up (at 12 months, p=0·4122). Quality of life improved in all four ASCRS scales (p<0·0001) and in seven of eight SF-36 scales, though only social functioning was significantly improved (p=0·0002). Interpretation Sacral nerve stimulation greatly improves continence and quality of life in selected patients with morphologically intact or repaired sphincter complex offering a treatment for patients in whom treatment options are limited.