BACKGROUND: : Sacral nerve modulation has been reported as a minimally invasive and effective treatment for constipation refractory to conservative treatment. OBJECTIVE: : This study aimed to evaluate the efficacy and sustainability of sacral nerve modulation for constipation in the medium term (up to 6 years) and to investigate potential predictors of treatment success. DESIGN: : We performed a retrospective review of prospectively collected data. SETTINGS: : The study was performed at 2 tertiary-care centers in Europe with expertise in pelvic floor disorders and sacral nerve modulation. PATIENTS: : Patients were eligible if they had had symptoms of constipation persisting for at least 1 year, if conservative treatment (dietary modification, laxatives and biofeedback therapy) had failed, and if predefined excluded conditions were not present. INTERVENTION: : The first phase of the treatment process was percutaneous nerve evaluation. If this was successful, patients underwent sacral nerve modulation therapy with an implanted device (tined-lead and implantable pulse generator). MAIN OUTCOME MEASURE: : Follow-up was performed at 1, 3, 6, and 12 months, and yearly thereafter. Outcome was assessed with the Wexner constipation score. RESULTS: : A total of 117 patients (13 men, 104 women) with a mean age of 45.6 (SD, 13.0) years underwent percutaneous nerve evaluation. Of these, 68 patients (58%) had successful percutaneous nerve evaluation and underwent implantation of a device. The mean Wexner score was 17.0 (SD, 3.8) at baseline and 10.2 (SD 5.3) after percutaneous nerve evaluation (p < .001); the improvement was maintained throughout the follow-up period, although the number of patients continuing with sacral nerve modulation at the latest follow-up (median, 37 months; range, 4-92) was only 61 (52% of all patients who underwent percutaneous nerve evaluation). The sole predictive factor of outcome of percutaneous nerve evaluation was age: younger patients were more likely than older patients to have a successful percutaneous nerve evaluation phase. LIMITATIONS: : The study was limited by a lack of consistent outcome measures. CONCLUSIONS: : Despite improvement in Wexner scores, at the latest follow-up sacral nerve modulation was only being used by slightly more than 50% of the patients who started the first phase of treatment. Further studies are needed to reassess the efficacy and sustainability of sacral nerve modulation.