Oral lichen planus is a relatively common disorder of the mouth that can be debilitating. It is frequently palliated with topical or systemic corticosteroids and retinoids. These treatments require prolonged use, however, and are not always effective. In a double-blind trial, 16 patients with symptomatic oral lichen planus were randomly assigned to receive either topical cyclosporine or its vehicle. The patients swished and expectorated 5 ml of medication (containing 100 mg of cyclosporine per milliliter) three times daily. After eight weeks, the eight recipients of cyclosporine had marked improvement in erythema (P = 0.003), erosion (P = 0.02), reticulation (presence of white lace-like lesions; P = 0.007), and pain (P = 0.002), whereas the eight recipients of vehicle had no change or minimal improvement. After a switch to cyclosporine for eight weeks, the vehicle-treated patients had improvement similar to that seen in the patients who initially received cyclosporine. There were no systemic side effects. In most cases blood cyclosporine levels were low or undetectable. Cyclosporine levels present in specimens of oral mucosa at the end of therapy four hours after the patients swished were similar to the levels previously reported in psoriatic lesions after treatment with systemic cyclosporine (14 mg per kilogram of body weight per day). As a topical preparation, cyclosporine may be useful in the treatment of oral lichen planus and possibly other cutaneous disorders. Oral lichen planus is a relatively common disorder affecting up to 2 percent of the general population.1 Any oral mucosal site may be involved, and there are usually multiple areas of involvement. Although reticular and papular lesions occur most frequently, they are usually asymptomatic and require no treatment.2 However, the erythematous and erosive forms of the disease can be a source of morbidity. In comparison with the cutaneous form of lichen planus, oral lesions are more resistant to therapy and less likely to undergo spontaneous remission. The primary goal of therapy for all forms of lichen planus is palliative. Three… © 1990, Massachusetts Medical Society. All rights reserved.