252 cases of odontogenic tumors treated for 21 years, from September 1970 to December 1992, at the Department of Oral Maxillofacial Surgery, Hokkaido University School of Dentistry were clinically analyzed on the basis of the 1992 WHO classification.<BR>1) The tumors were classified as ameloblastoma (52.4%), compound odontoma (18.6%) and complex odontoma (13.4%). The remaining 16% consisted of 5 cases of malignant tumors and 7 rare benign odontogenic tumors.<BR>2) Histopathologically, the ameloblastomas were classified as the follicular type in 49 cases (37%) and plexiform type in 75 cases (57%).<BR>3) Of the 252 cases, 161 were males and 91 were females, a 1.8: 1 sex ratio.<BR>4) The age at the first visit was generally between 10 and 30 years.<BR>5) 189 cases (75%) developed in the mandible and 63 cases (25%) in the maxilla. In most of the mandibular ameloblastomas, the lesions were very extensive, usually extending from the molar to the ramus region.<BR>6) 60% of the chief complains was swelling.<BR>7) Impacted teeth were found in 139 cases (55%).<BR>8) The surgical treatments employed for ameloblastoma were the “Dredging Method”, a conservative procedure, in 77 cases (58%), enucleation in 12 cases (9%), block resection in 10 cases (8%) and hemimandibulectomy in 5 cases (4%). Fifteen cases of ameloblastoma were recurrent.<BR>The surgical treatment usually employed for the other benign odontogenic tumors was enucleation. The “ Dredging Method” was employed in 5 cases where benign tumors, other than ameloblastoma, caused extensive destruction of the mandible. No sign of recurrence had been noted.<BR>9) Two patients with malignant ameloblastoma underwent surgical therapy. One died of uncontrolled tumor, and the other patient has survived for 20 years since surgery without recurrence. A pa-tient with primary intraosseous carcinoma that received surgical and radiation therapy has survived for 14 years since surgery without recurrence. A patient with ameloblastic fibrosarcoma has survived for 7 years since surgery without recurrence, but a patient with an unclassified malignant odontogenic tumor died of uncontrolled tumor after surgery.