Method: Forty cases clinically diagnosed as oral leukoplakias and that presented a mild to intense degree of epithelial dysplasia and could not be diagnosed as any other disease were selected. Twenty cases were from current smokers (more than 20 cigarettes/day for at least 1 year) and neversmokers. Thirty-six cases of leukoplakia without dysplasia were used as controls. Histological sections of each lesion were subjected to the estreptoavidin biotin immunohistochemical method for detection of p27.