In operative treatment of extensive tumors of the lateral oropharyngeal region a combination of hemimandibulectomy and radical neck dissection (composite operation) is often necessary. The morphological and functional effects of hemimandibulectomy on the remaining temporo-mandibular joint are examined by clinical and radiological studies in 7 cases. Immediately after operation the patient will have problems with feeding, speech, adaptation of the prosthesis, occlusion and articulation. However, compensation will develop to a large extent. From our late results we conclude that these difficulties are so small that plastic reconstruction of the removed mandible does not appear urgent. Postoperative irradiation should always be undertaken, if the histology of the tumor proves to be radiosensitive, regardless of the complications for a later plastic reconstruction. The postoperative deviation of the mandible is reduced in edentulous patients with the help on an inclined plane. If the teeth are preserved, postoperative fixation with elastic ligatures is done as soon as possible in order to adjust slowly the position of the mandible to achieve central occlusion.