This study comprises 30 patients with extensive oral cancer invading the mandibular bone. In each case, large segmental composite resections were performed and the mandibles primarily reconstructed, according to the principles of rigid internal fixation. All but one of the reconstructions were successful and the functional and cosmetic results were excellent or good in 12 patients. The results indicate that primary reconstruction can be performed without major complications. Bone transplantation may be omitted or postponed to a later date. The fact that tracheostomy and intermaxillary fixation can be avoided, is a major advantage for these patients.