Oral leukoplakias are oral potentially malignant disorders in which toluidine blue can be used to identify important sites to be performed a biopsy as these sites could show epithelial dysplasia.Thirteen patients with white patches located in the oral mucosa were included in this study. Thus, to determine sites that could show epithelial dysplasia, toluidin blue was used on the leukoplakias to better guide their biopsies. In addition, all of cases exhibiting epithelial dysplasia were investigated, by immunohistochemistry, for Ki-67 and Cyclin d1.Toluidine blue identified leukoplakias showing mild, moderate and severe epithelial dysplasia. Those cases with severe epithelial dysplasia showed particularly toluidine blue staining (p=0.061) and increased Ki-67 index (p<0.001). The histological grading of epithelial dysplasia and immunostainnig for Cyclin d1 were not associated (p=0.506) in this study. It is important to state that all those patients have been followed for three years and up to date one case marked as severe dysplasia previously treated by means of surgery had changed into an oral squamous cell carcinoma.Toluidine blue seems to be useful to guide oral leukoplakias biopsies showing variables grades of epithelial dysplasia, especially severe grading, as these alterations contributed to increase Ki-67 index.