In a selected patient group(idiopathic faecal incontinence or incontinence as a result of an external anal sphincter tear (<160 degrees)) we have evidence that 90% of patients will have a successful test period (≥50% reduction in incontinence episodes). If preoperative there is motor response on at least 3 out of 4 poles on the lead, at a threshold ≤1.5 mAMP(unpublished data, submitted for publication) .