The intraoperative knowledge of margin status on mandibulectomy specimens is important for primary reconstruction. The goal of this study was to evaluate whether intraoperative bone marrow (BM) curettings and inferior alveolar nerve (IAN) biopsies are representative of final decalcified cross-sectional (shave) mandibular bone margins. Forty-seven margins in 27 patients consecutively treated with segmental mandibulectomy for squamous cell carcinoma were reviewed. These patients had BM or IAN margins sampled by surgeons and assessed intraoperatively by routine frozen section. The full cross-section of mandibular bone margins were sampled by pathologists at the time of routine gross examination. Intraoperative evaluation of BM/IAN biopsies is characterized by a 50% sensitivity (3 of 6 cases were false negative) and a 100% specificity. IAN biopsies are representative of the final bone margin. Given the technical feasibility of intraoperative BM and IAN assessment, we favor routine intraoperative evaluation of mandibular bone margins. However, even when bone margins are sampled intraoperatively, obtaining a full cross-section of the bone margin at the time of gross examination should also be performed as it remains the most accurate modality of bone margin assessment.