The expression of Ki-67 antigen of ameloblastoma was examined in order to investigate the different proliferation activity of histological variants of ameloblastoma and its clinical significance.70 cases of different histological specimen of ameloblastoma were analyzed by immunohistochemical method using Ki-67 antibody. The Label Index was calculated in percentage of Ki-67 positive cells after examined with an image analysis system.The results showed that the Labeled Index in malignant ameloblastoma was the highest 14.72% +/- 2.87%. The Labeled Index in solid ameloblastoma was in the middle, among which the follicular 4.42% +/- 1.05% was higher than the plexiform 3.64% +/- 1.23%. The Labeled Index in mono-cystic ameloblastoma was the lowest 2.21% +/- 1.09%.The results demonstrated that the proliferation activity varied according to the histological pattern of ameloblastoma. The prognosis with different proliferation activity was also varied accordingly.