Objectives: To investigate the molecular expressions on cell proliferation and tumor invasion.Methods: 15 cases of CEOT were collected from 1970 to 2003. All tumors were stained with HE, PAS and Conge red.The ultrastructure of one fresh tumor was also observed. The expression of molecules relative to cell proliferation or tumor invasion, including PCNA, bcl-2, NF-kB, MMP2, MMP9, TIMP1, TIMP2 were examined by immunohistochemical SP and in situ hybridization technique.Results: 10 tumors were intraosseous lesions and 5 tumors were extraosseous lesions. Nine out of fifteen showed local invasion features. Ultrastructurally, tumor cells and nuclei showed pleomorphism. The homogeneous substance consisted of dense accumulations of granulo-fibrillar material. PCNA was expressed in 13 cases of CEOT and bcl-2 protein was broadly located in tumor cells. The nuclear positive rate(8.7 percent) of nuclear factor kB subunit p65 in tumor cells was higher than in normal oral mucosa. MMP2 was expressed in 3 cases of local invasive CEOT. The positive rate of MMP9 was higher than that of MMP2. TIMP2 was located in tumor cells and stroma of all CEOTs. There was no significant difference between invasive and no local invasive CEOTs. MMP9 mRNA showed higher positive level and broader distribution than MMP9 protein did. TIMP1 mRNA and its protein mainly distributed in tumor cells and nearly were negative in stroma. Conclusions: CEOT tumor cells showed high proliferating activity, and the correlation between NF-kB subunit p65 and bcl-2 suggested NF-kB could bind to kB site of bcl-2 to regulate its transcription. The high level of bcl-2 also indirectly showed that tumor cells had high proliferating activities. MMP, TIMP and NF-kB participated in the process of invasion in CEOT; furthermore, it seemed that MMP9 and TIMP1 were more relative to invasion of CEOT. Whether NF-kB regulated MMP gene in CEOT was not determinate.