The lichen planus is a mucocutaneous disease with unknown etiology and auto-immune pathogenia. There have been three variants of lichen planus: the reticular, the plaque-like and the atrophic-erosive lesions. It?s a chronic disease with acute relapses that generally affects more frecuently to women from the fourties. The diagnostic is based on the clinic identification of the lesions joined with the histopathologic study (basal cells hidropic degeneration, linfoplasmocitic infiltration and absence of displasy signs). The great number of therapeutic options are explained for its high prevalency (0.5-2%), its recurrence and its risk for malignant transformation. We present a case of oral erosive lichen planus, refractory to numerous treatments, mainly corticosteroids. During 15 days the lesion responded to the administration of a 0.1% tacrolimus in topic application. This article tries to show the new indication of tacrolimus, a calcineurin inhibitor immunosuppressor, that it is effective in the erosive lesions treatment.