The malignant transformation of lichen ruber planus (LRP) is a quite frequent event for which, at present, no clear pathogenetic explanation has been given. Recently, attention has been paid to growth factors and growth factor receptors as possible pathogenetic factors of malignancy, even if not enough studies have been performed to exploit their role in oral diseases. Aim of the present study was to investigate the expression of epidermal growth factor receptor (EGFr) in squamous carcinomas arising in patients with LRP. The study has been performed on formalin-fixed, paraffin-embedded tissue biopsies obtained from 11 patients with previous diagnosis of LRP in which squamous carcinoma had developed. A monoclonal anti-EGFr antibody has been used, with the ABC technique, on histological sections. EGFr has been immunolocalized in basal and suprabasal epithelial layers in LRP with the highest intensity of staining in the areas with strong inflammation. EGFr immunostaining could be detected in dysplastic areas as well, even if the intensity of staining seemed to decrease with severity of dysplasia. In well-differentiated squamous carcinoma EGFr was intensely expressed, especially in mature keratinized cells. Weaker or absent EGFr immunoreaction was detected in moderately and poorly differentiated carcinomas. The results of the present study seem to show that EGFr is expressed in squamous carcinomas arising from LRP. The variability of EGFr expression in inflamed oral mucosa, in dysplastic areas and in tumors with different degrees of differentiation seem to point out that EGFr might somehow regulate the maturation and replication of epithelial cells in LRP and in its malignant counterpart. The speculations achieved from the present study need further evaluation on wider series of cases and, possibly, with different antibodies which would allow the identification of mutant forms of the receptor.