The course of reticular, papular, bullous, plaque-type, atrophic and ulcerative lesions of oral lichen planus (OLP) was studied in 611 patients. Mean age of the patients was 53 years and two-thirds were women. The patients were followed for periods from 1 to 26 years (mean, 7.5 years). The various clinical types had somewhat different courses. Papular affections were seen mainly in the initial phase and had a transitory course. Ulcerative lesions, although more persistent, also generally showed a short-term course. The atrophic form was fluctuating with many remissions and new-established affections. The plaque-type was a more constant form, but also demonstrated many newly established affections. After a few years, many patients had persistent lesions that no longer included the affections most characteristic of OLP, i.e. the reticular and the papular form. Initial presence of papular affections was associated with ages below 50 and atrophic lesions with ages above 60. Plaque-type affections were seen with a significantly higher frequency among tobacco smokers at the onset of OLP. No other correlation was found between the initial presence, the remission and the development of the different clinical forms and various factors as age, sex, general diseases, medication and tobacco smoking. Treatment with topical steroid and/or antimycotics had no effect on the long-term course of the various clinical forms, and it had no persistent effect on symptoms related to OLP. Complete remission was seen in 17% of the patients, and it showed a reverse association with the initial presence of plaque-type affections. However, complete remission was associated with an initial presence of papular affections.(ABSTRACT TRUNCATED AT 250 WORDS)