Squamous cell carcinoma (SCC) is the commonest cancer in the mouth. Multiple risk factors, such as smoking, alcohol consumption, irradiation, viruses infection and chronic irritation are thought to be responsible for the formation of oral squamous cell carcinoma. Although SCC can develop through a series of precancerous stages manifested as various degrees of epithelial dysplasia, this is not always the case. p53 is the commonest mutated gene in human cancers. Mis-sense mutation of the gene or complexing of the protein with viral or cellular proteins prolongs its half-life and leads to its detection by immunohistochemistry. This study was designed with the aim of demonstrating any possible relationship between p53 and oral squamous cell carcinoma by immunohistochemical staining techniques. A total of 66 specimens from the oral cavity (10 normal mucosa, 11 hyperkeratosis without dysplasia, 11 mild dysplasia, 11 moderate dysplasia, 10 severe dysplasia and 13 SCC) were examined for the presence of p53. The results show p53 was not expressed in normal mucosa, but was found with increasing frequency in increasingly severe dysplasia and SCC. In conclusion, this study shows p53 mutation is common in oral squamous cell carcinoma and probably occurs early in the multisteps of oral carcinogenesis.