Autogenous bone grafting is the gold standard for reconstructing craniofacial defects. Mandibular defects are reliably reconstructed with free nonvascularized bone, such as from the posterior iliac crest (PIC). In light of improved imaging, including 3-dimensional computed tomography scanning, a more accurate defect estimation is possible. A strong understanding of bone graft available is necessary. The purpose of this study was an updated review of the dissection and quantification of the amount of bone that can be safely harvested. Bilateral bicortical osteotomy was performed on 55 cadavers to obtain 110 PIC bone grafts. Demographic factors and bicortical osteotomy measurements were recorded. Average osteotomy lengths, widths, and depths were 7.4, 5.5, and 1 cm, respectively. The average bicortical osteotomy volume was 40.6 cm3. During the dissection, the authors identified 2 anatomical variants with respect to muscle insertion into the PIC. In variation 1, which occurred in 62% of dissections, the latissimus dorsi and thoracolumbar fascia did not originate from the PIC. When this occurred, the quadratus lumborum attached to the PIC. In variation 2, which occurred in 38% of dissections, the latissimus dorsi and thoracolumbar fascia originate from the PIC. By identifying the maximal bone volume obtainable from a PIC graft and noting 2 anatomical variants, this study allows for more accurate surgical planning and management.