Involvement of the mouth in the ordinary type of lichen planus is a commonplace occurrence. Involvement of the mouth alone by this disease is, however, uncommon and causes many to hesitate to make the diagnosis unless it is corroborated by histologic examination. During the past eight years I have had a series of ten such cases which is somewhat unusual in that biopsies were performed in six of them, seven were presented before a dermatologic society, and all have been followed up to the time of writing. In this communication I shall describe the frequency, diagnosis, duration and response to treatment of lichen planus confined to the mouth. ANALYSIS OF CASES In my series of ten cases, nine occurred in private patients and one was seen at the University and Bellevue Clinic. Four of the patients were men and six women; their ages varied from 23 to 55, the