In the course of ilioinguinal exposure, significant bleeding can occur from anastomotic vascular channels along the posterior aspect of the superior public ramus. A cadaveric study was undertaken to quantify and qualify these communicating vascular systems. We made bilateral ilioinguinal exposures on 40 cadavers. All vessels > 2 mm in diameter, connecting the obturator system with a more superficial system, were singled out and their courses recorded. Fifty-eight of 79 sides (73%) had at least one large-diameter communicating vascular channel along the posterior aspect of the superior pubic ramus. In 47 of the 79 exposures (59%) communicating veins were noted. Arterial channels were identified in 34 exposures (43%). A prospective clinical study was also performed. Thirty-eight consecutive patients with displaced acetabular fractures were treated surgically using ilioinguinal exposures. Fourteen of the patients (37%) had anastomotic vessels. This study confirms the variability of the retropubic vascular system.