Surgeons who perform robot-assisted laparoscopic prostatectomy (RALP) would know that working in relatively narrow pelvic cavity may sometimes make robotic arms brush up against each other or graze by pelvic wall or other structures. Such effects may contribute to prolonged operative time and/or increased blood loss, possibly resulting in adverse outcomes. Thus, we evaluated the effect of bony pelvic dimensions measured via preoperative magnetic resonance imaging (MRI) on performing RALP.