Objectives To evaluate the difference in outcome of bladder neck contracture (BNC) and its causes among large groups of patients undergoing open radical prostatectomy (ORP) and robot-assisted laparoscopic prostatectomy (RALP). Patients and Methods We analyzed 200 consecutive RPs performed by one surgeon for prostate cancer, 100 by ORP, and 100 by RALP, between March 2003 and September 2007. The operative techniques of bladder neck repair and urethrovesical anastomosis were different. The ORP patients had a conventional stomatization and “racquet handle” repair of the bladder if necessary, with mucosal eversion and a direct circular interrupted “end-to-end” suture anastomosis between the bladder and urethra. The RALP patients had no bladder neck reconstruction or mucosal eversion and their anastomosis was by the continuous suture “parachute” technique. Results There was no BNC in the RALP group, whilst 9% of the ORP group developed a BNC (P Conclusion This series suggests that the major factor involved in the cause of bladder neck contracture after ORP relates to the stomatization or “racquet handle” bladder neck repair, and the end-to-end anastomosis between the urethra and stomatized bladder. Mucosal eversion might also contribute. Normal postoperative urinary leakage when the anastomotic apposition is good seems unlikely to be a significant etiological factor in the development of BNC. Prolonged urinary leakage results from an anastomotic gap, which heals by second intention, thereby causing scarring and BNC. The RALP “parachute” technique, which expands the anastomosis towards the bladder, appears to protect against BNC. Mucosal eversion is not necessary in the parachute repair.