Major vascular injuries complicating laparoscopic operations are a source of significant morbidity and mortality. The goal of this study was to measure the distances between the anterior abdominal wall subumbilical trocar entry site and the retroperitoneal location(s) of the aorta, iliac vessels, and urinary bladder directly. Patients were measured during actual laparoscopic surgery in the lithotomy, or modified lithotomy position, level, and Trendelenburg positions. Patients were all divided according to body-mass index (BMI) and height. Significant differences between distances from the primary trocar insertion site to the aorta and the iliac vessels were observed. Similarly, significant differences in the thickness of the anterior abdominal wall were observed between three BMI groups. The use of reasonable precautions will enable the surgeon to avoid trocar damage to the great vessels located in the abdominal retroperitoneum. (J GYNECOL SURG 18:121)