Ankylosis is an uncommon disease of the temporomandibular joint (TMJ), the effective treatment of which requires detailed preoperative evaluation of the type and extent of the deformity. As well as lateral radiographs and computed tomography (CT), three-dimensional CT has been introduced to improve the preoperative evaluation. We present six patients with ankylosis of the TMJ who were evaluated by three-dimensional CT before and after condylectomy. Preoperative findings were compared with operative findings. Three-dimensional CT provides a detailed three-dimensional image of the TMJ non-invasively and we suggest that it is a valuable tool for evaluation of ankylosis in the TMJ.