Oral hairy leukoplakia was first described in homosexual men infected with the human immunodeficiency virus. It is thought to be caused by infection with both the Epstein-Barr virus and human papillomavirus. We report 59 cases of oral hairy leukoplakia. The disease was diagnosed in patients in all risk groups and was categorized in all classes of the Walter Reed classification without significant differences in prevalence. Epstein-Barr virus could be demonstrated in all tissue samples examined; human papillomavirus was found in only a few specimens. In our series oral hairy leukoplakia had a chronic course, although temporary spontaneous healing occurred in some cases. Its appearance was a poor prognostic sign because acquired immunodeficiency syndrome developed in a significant proportion of patients within a few months of onset.