Anterior sphincter repair for faecal incontinence related to obstetric trauma was performed in 55 patients: 32 with incontinence after delivery and 23 with late onset. Anal endosonography and physiological tests were performed before and after surgery. After a median of 15 (range 6-36) months, 42 patients had improved, 11 had not improved and two were awaiting colostomy closure. The postoperative squeeze pressure was increased (by 20 versus 5 cmH2O, P = 0.05) and the external sphincter was more frequently intact (32 of 35 versus five of 11, P = 0.003) in those with a good outcome. Patients with an intact external sphincter had higher postoperative squeeze pressures (50 versus 20 cmH2O, P = 0.004). Patients with late-onset incontinence were older than those who developed incontinence soon after delivery (median 59 versus 32 years, P < 0.001) and had longer pudendal nerve terminal motor latencies (2.3 versus 2.1 ms, P = 0.03). Failure of repair is related to persistent external sphincter defects. Late-onset incontinence, even with a prolonged pudendal nerve terminal motor latency, does not preclude a good outcome.