Discontinuity defects of the mandible have been successfully treated by means of cancellous-marrow grafting techniques. This method of reconstruction has not been widely reported in the repair of defects in mandibles that have been exposed to radiation therapy. In the two cases presented in this article, the patients were previously treated for oral squamous-cell carcinoma by irradiation and partial mandibulectomy. Later, cancellous-marrow grafts were implanted. One patient received 3,000 rads of Cobalt-60 and had the body of the right mandible resected. The subsequent grafting procedure was successful in this patient. The second patient received 6,000 rads of Cobalt-60 and underwent resection of the mandible anterior to the molar region. The subsequent graft failed in this case.