Background: Oral lichen planus is a chronic mucocutaneous disease of uncertain etiology. Inflammatory cell infiltrate plays an important role in pathogenesis of oral lichen planus. It is said that hyperplastic epithelium is seen where the inflammatory cell infiltrate is mild while beneath atrophic epithelium dense inflammatory cell infiltrate is evident. Studies have shown negative correlation between thickness of the epithelium and thickness of inflammatory cell infiltrate. Morphometric studies in oral lichen planus are very scanty and have been performed using stage micrometer and eye piece graticule. Using Image Analysis Software can avoid inter-observer variations which has not been done till date. Aim and Objectives:The present study aimed at evaluating thickness of epithelium and thickness of inflammatory cell infiltrate and to determine any existing relation between the same using Image Analysis Software. Other histopathologic features were also evaluated.Materials and method: 58 confirmed cases of oral lichen planus from buccal mucosa were retrieved from department archives. 6µ thick sections were stained with Hematoxylin and Eosin. Six non-overlapping fields were selected randomly from each section and photomicrographs were captured under 4x objective using Trinocular Research Microscope. Morphometry was done using Image Analysis Software and data was stored in Microsoft excel for statistical analysis. Results:In present study the mean of epithelium thickness was 281.2059 and inflammatory cell infiltrate thickness was 330.2540. An inverse correlation was observed. As the thickness of inflammatory cell infiltrate increased there was a decrease in thickness of epithelium (Coefficient -0.156). Conclusion:Thickness of the epithelium may vary according to the site, however in this study all cases were from buccal mucosa. Inflammatory cell infiltrate influences overlying thickness of epithelium and determines its nature. How to cite this article:Ramya VV, Nandini DB, Praveen SB, Madhushankari GS. Thickness of the epithelium and the inflammatory cell infiltrate in oral lichen planus. A morphometric study. CODS J Dent 2014;6;78-82 Source of support: Nil. Conflict of interest: None Declared.Hyperplasia, acanthosis, hyperkeratosis are usually observed phenomena in the epithelium in oral lichen planus. The underlying inflammatory cell infiltrate influences the nature of epithelium as observed in this morphometric study.