Vital to the study of past populations and an important phase in executing a forensic anthropological examination is the determination of skeleton sex. The aim of this study is to present an easy and reliable criterion for sexing the skeleton. The ilium and sacrum of 2845 skeletons were examined for new bone formation and for bridging/fusion in/across the sacroiliac joint. Sacroiliac joint bridging (SIB) was present in 12.27% of the males and 1.83% of the females. In 97% of the males bridging was extra-articular, whereas in all females bridging was intra-articular. In addition, computed tomograghy images of 81 in vivo individuals were examined for the same phenomenon. SIB was present in 34.2% of the males and 4.6% of the females. Bony spurs present on the ilium for a preliminary partial or full extra-articular bridging of the sacroiliac joint indicate a male skeleton. SIB presents an easy technique for sexing skeletons (especially in elderly individuals where the phenomenon of SIB becomes very common), as no prior knowledge, training, or equipment is required to apply the criterion.