Objective: To investigate the expression of P16 protein in oral verrucous carcinoma (VC) and oral squamous cell carcinoma (SCC) and to reveal its role in the occurrence and development of VC . Methods: Using streptavidin/peroxidase(SP) immunohistochemical technique(IHC) the expression of P16 protein in 41 samples, including 8 of normal mucosa (NM),13 VC,10 well differentiated squamous cell carcinoma (wdSCC),10 poorly differentiated squamous cell carcinoma (pdSCC) was studied.The average intensity score (IS) of immunohistochemical staining of the samples was calculated. Results: Weakly positive of P16 protein was obsereved in the 8 cases of NM. Positive expression was found in 10 of the 13 VC cases,8 of the 10 wdSCC and 6 of the 10 pdSCC.The IS in NM,VC, wd SCC and pdSCC was 0.4375?0.0498,1.5846?0.2681,0.9900?0.1894 and 0.8800?0.2590 respectively.The mean intensity of P16 protein in VC was higher than in wdSCC and pdSCC(P