Betamethasone valerate aerosol, given in doses of up to 800 microgram per day, was compared with placebo in a double-blind trial involving 23 patients with oral lichen planus. The majority of patients receiving the active aerosol noted improvement within the first 2 weeks of treatment and at 8 weeks the lesions had almost cleared; in contrast, only 2 patients on placebo showed slight improvement over the same time period. The results suggest that this form of treatment is an effective and acceptable method of controlling the discomfort due to oral lichen planus, especially where minor erosions are present.