The authors report the results of a study performed in 71 patients suffering from lichen planus of the mucous membranes and skin. They discuss dermatological and stomatological clinical data in relation to possible basal diseases (hepatopathies, dermopathies, diabetes, hypertension, gastrointestinal diseases, etc.) and other anamnestic data (psychological aspects, drug taking, working activity, etc.). Moreover, they report the results of the clinical protocol used (betamethasone in a gel and vitamin A base) with a follow-up of 5 years and examine the other therapeutic possibilities reported in the literature.