The bony pelvis provides more obvious sex differences than any other bone in the human skeleton. This study evaluates a bony extension of the medial aspect of the greater sciatic notch, which extends caudad to the arcuate line as seen on pelvic radiographs. A total of 2620 randomly selected supine pelvic radiographs (anteroposterior view) of adult females and males were reviewed. The subjects belonged to a central Anatolian population and their age ranged between 18 and 77 years in females and between 18 and 81 years in males. Only 22 (1.7%) of the 1337 female pelvic radiographs showed a bony extension, whereas 882 (68.8%) of the males had one. All these bony extensions were bilateral and symmetric. The results were statistically significant (P < 0.001). We assert that this radiographic appearance is a male characteristic.