Oral lichen planus is an inflammatory disease with mucous and cutaneous affects caused by cellular immune reaction. Basal cell vacuolation degeneration is the result of T-cell aggression. As the clinical and histopathological alterations of OLP range from epithelial hyperplasia to epithelial atrophy and erosion, it could be that different forms of OLP finally express differences in the intensity of immune attack. The aim of the present study was to analyse the relationship between the clinical and histopathological behaviour and the intensity of the immune response to OLP by means of basal cell vacuolation and inflammatory infiltrate intensity measurement. We analysed 47 patients with OLP. Requirements for inclusion were histopathological diagnosis of OLP from an oral biopsy. Clinical and histopathological correlations were made. OLP's with an intense inflammatory infiltrate were correlated with a high grade of basal cell vacuolations (p < 0.01). A positive statistical correlation between basal cell vacuolation and epithelial atrophy (p < 0.01), and between inflammatory infiltrate intensity and epithelial atrophy (p < 0.01) were observed. An inverse statistical correlation was found when the inflammatory infiltrate intensity and the degree of basal cell vacuolation were compared with epithelial hyperplasia (p < 0.05 and p < 0.01 respectively). In the present study, OLPs with intense immune aggression frequently show epithelial atrophy and erosion on microscopic examination and vice versa.