Previous studies showed that daily low dose sildenafil leads to improvement of the preservation of nocturnal penile tumescense and rigidity (NPTR) 6 weeks after nerve-sparing radical prostatectomy (nsRP). Aim of this study was the evaluation of NPTR-preservation on further erectile function (EF) recovery in the long term follow-up. 24 sexual active patients were operated by nerve-sparing radical prostatectomy. An erectometer measurement of NPTR (Rigi-Scan®) was carried out on each patient after removal of the transurethral catheter and again 6 weeks after surgery. To maintain and support recovery of spontaneous erectile function 12 patients with preserved nocturnal erections detected during NPTR-recordings received sildenafil 25mg/d at night starting immediately one the day after catheter removal (group 1). A control of 12 patients underwent follow up without daily PDE-5-inhibitors (group 2). All patients completed an IIEF-5 questionnaire concerning erectile function preoperatively, 3, 6, 12, 18 and 24 months after surgery.