Statement of the Problem: Oral lichen planus (OLP) is a chronic inflammatory disorder with various clinical features; however, its pathogenesis is still unknown. In OLP, destruction of the basement membrane and migration of T-cell may be mediated by matrix metalloproteinases.Purpose: The aim of this study was to examine the role of stromelysin-2 (ST-2) expression in pathogenesis of OLP.Materials and Method: A retrospective analysis of 46 samples including 26 patients with OLP and 20 control patients with oral irritation fibroma was performed. All samples were stained employing immunohistochemistry method. After immunohistochemical staining for ST-2 marker and microscopic examination of the samples, the expression levels of ST-2 were evaluated. The data were analyzed by SPSS (V.21) and applying Mann-Whitney test.Results: The strength of ST-2 expression was seen in most cases of OLP group, whereas control group did not show ST-2 expression. Mean expression of ST-2 in connective tissue was 1.7±1.10 and in the epithelium of the OLP samples was 1.6±1.06. Likewise, the ST-2 expression in connective tissue and epithelium of the OLP erosive lesions was significantly higher in comparison with reticular lesions (p< 0.05).Conclusion: According to the results of this study, we suggest that ST-2 may be involved in the formation of OLP lesions and it may play a key role in the transformation of reticular to erosive form of OLP. Keywords ● Oral lichen planus  ● Stromelysin-2  ● Pathology