As it is an unusual and infrequent clinical entity, hyperplasia of the coronoid process is often overlooked or diagnosed too late. The aim of this study was to characterize the morphology, etiology, and clinical picture of coronoid hyperplasia as well as to discuss its diagnosis and treatment.All cases of histologically confirmed hyperplasia of the coronoid process treated in our center between 1995 and 2004 were analyzed. Patient data were evaluated with respect to age, gender, clinical symptoms, diagnostic work-up, and treatment. The extracted data were compared to those found in the literature.The study included 14 new cases and 101 cases already published: 96 with bilateral and 19 with unilateral hyperplasia. At the time of diagnosis, the subjects' mean age was 23.7 years. The patients in Bonn were all treated by coronoidectomy and appropriate physiotherapy. An improvement in mouth opening could be achieved in 86% of our patients.In comparison to the somewhat disappointing results of previously published studies with regard to mouth opening and mandibular mobility, our treatment concept seems to offer the possibility for improvement. Our study emphasizes the significance of three-dimensional CT techniques for diagnosis and surgical planning, the superiority of coronoidectomy over coronoidotomy, and the importance of dynamic physiotherapy to prevent postoperative scar formation.