Summary A review of the literature indicates that only 12 cases of unilateral enlargement and three previous cases of bilateral enlargement of the coronoid process have been recorded. The clinical features, differential diagnosis, radiographic appearances, and pathology of these conditions are discussed. The importance of considering abnormality of the coronoid process as a causative factor in limitation of mandibular movement is emphasised. Methods of treatment previously employed are considered. Two case reports of bilateral enlargement are described, one of which was the subject of an operation employing an intra-oral approach. The development of the coronoid process is considered with reference to the insertion of the temporalis tendon and the conclusion is reached that unilateral enlargement generally takes the form of an exostosis or, more rarely, an osteoma or osteochondroma but that bilateral enlargement is due to developmental hyperplasia. The value of the intra-oral approach for the removal of bilateral enlargement of the coronoid process is pointed out.