Background: Sacral nerve stimulation has been approved for use in treating urinary incontinence in the United States since 1997, and in Europe for both urinary and fecal incontinence (FI) since 1994. The purpose of this study was to determine the safety and efficacy of sacral nerve stimulation in a large population under the rigors of Food and Drug Administration-approved investigational protocol. Methods: Candidates for SNS who provided informed consent were enrolled in this Institutional Review Board-approved multicentered prospective trial. Patients showing ≥50% improvement during test stimulation received chronic implantation of the InterStim Therapy (Medtronic; Minneapolis, MN). The primary efficacy objective was to demonstrate that ≥50% of subjects would achieve therapeutic success, defined as ≥50% reduction of incontinent episodes per week at 12 months compared with baseline. Results: A total of 133 patients underwent test stimulation with a 90% success rate, and 120 (110 females) of a mean age of 60.5 years and a mean duration of FI of 6.8 years received chronic implantation. Mean follow-up was 28 (range, 2.2-69.5) months. At 12 months, 83% of subjects achieved therapeutic success (95% confidence interval: 74%-90%; P < 0.0001), and 41% achieved 100% continence. Therapeutic success was 85% at 24 months. Incontinent episodes decreased from a mean of 9.4 per week at baseline to 1.9 at 12 months and 2.9 at 2 years. There were no reported unanticipated adverse device effects associated with InterStim Therapy. Conclusion: Sacral nerve stimulation using InterStim Therapy is a safe and effective treatment for patients with FI.