Background: Oral lichen planus (OLP) is categorized as premalignant lesion although its malignant potential is a matter of controversy. The objective of this study was to investigate Ki67 expression in OLP, oral epithelial dysplasia and oral squamous cell carcinoma (OSCC). Materials and Methods: Expression of Ki67 was evaluated through immunohistochemistry (IHC) in groups of A (17 cases of epithelial hyperplasia), B (16 cases of OLP), C1 (10 cases of mild epithelial dysplasia), C2 (10 cases of severe epithelial dysplasia), D1 (10 cases of well-differentiated OSCC), and D2 (10 cases of poorly-differentiated OSCC). Results: There was a significant difference in Ki67 expression based on quantitative analysis among the six studied groups as well as group B compared bilaterally with groups C2, D1 and D2 (p< 0.0001). However, there was no significant difference between groups B and C1 or between groups D1 and D2 (p> 0.05). Conclusions: Based on the results of the present study it may not be possible to definitely consider malignant transformation potential for OLP. However, expression of Ki67 was significantly higher in OLP than that of epithelial hyperplasia with no significant difference from that of mild epithelial dysplasia. This should be considered by clinicians to carefully and regularly follow up OLP lesions to detect potential subtle changes at an early stage.