The monoclonal antibody Ki-67 detects a nuclear antigen that is present only in proliferating cells. This is of particular interest for the analysis of the proliferation rates of malignant tumors. The aim of this study was to investigate the malignant potential of oral lichen planus (OLP) on the basis of expression of Ki-67 in healthy individuals (HI), patients with OLP and patients with squamous cell carcinoma (SCC), and to see for any potential interdependence between Ki-67 expression and different clinical and histopathological parameters in OLP.Immunohistochemistry for Ki-67 was carried out using an avidin-biotin peroxidase complex method.Ki-67 was more expressed in keratinocytes and lymphocytes of OLP patients compared with HI, but less compared with patients with SCC. Keratinocytes and lymphocytes stained with Ki-67 in OLP patients were significantly higher in males, and in OLP specimens showed less developed civatte bodies (CB) and thickening of the basal membrane (TBM).Ki-67 may not serve as prognostic biomarker in oral cancer development from the initially diagnosed OLP, but it could help selecting patients with higher need of follow up for prevention of malignancy.