Five hundred seventy patients with oral lichen planus were followed for periods ranging from 6 months to more than 10 years (mean, 5.6 years). The mean age was 52 years, and 67% of the patients were women. Erosive lichen planus was the most frequent clinical form, and the buccal mucosa was the most common site. Of the 75% patients treated with corticosteroids, 29% experienced complete remission and 63% had partial remission while maintained on medication. Fewer than 3% experienced spontaneous remission. Malignant transformation occurred in 7 patients (1.2%) in a mean time of 3.4 years after the onset of lichen planus. The onset of lichen planus could not be associated with any evident factors, such as family history, Candida albicans, glucose intolerance, and smoking.