Nine patients suspected of having primary ameloblastoma of the mandible or maxilla and five patients with clinical and/or radiologic indications of postoperative recurrence of ameloblastoma were examined with magnetic resonance (MR) imaging. In the former, results were compared with those of conventional radiography, computed tomography (CT), and pathologic analysis. Seven tumors were multilocular; two were unilocular. MR imaging showed a mixed pattern of solid and cystic components (n = 9), irregularly thick walls (n = 9), and papillary projections (n = 6). MR imaging was superior to conventional radiography and CT in demonstrating these findings. However, shell-like bulgings of the bone cortex were demonstrated more effectively with conventional radiography and/or CT in six cases, and soft-tissue invasion was overestimated with MR imaging in four cases. All tumors except one showed strong enhancement of solid components including papillary projections, walls, and septa at enhanced MR imaging. In the latter group of patients, MR imaging correctly demonstrated recurrence in two and no recurrence in three.