砄bjective:To study the characteristics of proliferation and differentiation of malignant ameloblastoma.Methods:The expression of PCNA,Ki 67, CK19 and CK10 and CK13 proteins in 17 cases of malignant ameloblastoma was detected immunohistochemically by SP method. Results: The proliferating indices of PCNA and Ki 67 were significantly higher in malignant ameloblastoma than those in benign ameloblastoma ( P