Ameloblastoma is cytologically a benign tumor, but is clinically characterized by infiltrative growth and high recurrency. The criteria for surgical treatment of ameloblastoma has not yet established and it is generally accepted that ameloblastoma be treated differently based on clinical types. The purpose of this paper is to consider effectiveness of enucleation in large-sized intraosseous ameloblastoma that has treated more frequently by radical treatment. 39 cases of the intraosseous ameloblastomas were treated by enucleation in the department of oral and maxillofacial surgery of Yonsei University, dental college from February 1990 to January 2001. 25 cases were selected because they were large in size that could produce facial disfigurement or pathologic fracture of jaws. They were radiographically characterized by the cortical bone that was expanded or eroded locally and histopathologically by 19 solid ameloblastomas and 6 intramural type of unicystic ameloblastomas. Among the 25 cases, 4 cases - 3 solid ameloblastomas and 1 intramural type of ameloblastoma - recurred. Recurrence rate was 16%. The compact bone which is not invaded by ameloblastoma was used as surgical margin of enucleation with accompanying chemical cauterization for killing the residual tumor cells. This may have been the reason for the low recurrence rate. So, it is considered that enucleation and long-term follow-up enable the large-sized intraosseous ameloblastomas that were characterized by almost destroyed cancellous bone and expanded or discontinued cortical bone to treat minimizing facial disfigurement and masticatory dysfunction and sociopsychological impact produced by radical treatment. I recommend that the large-sized intraosseous ameloblastomas without involvement to the surrounding soft tissues be first treated by enucleation.