Suprabasal expression of Ki-67 is assessed as a marker for oral dysplasia. The study involved non-neoplastic epithelium adjacent to 74 oral squamous cell carcinomas. An immunohistochemical technique was carried out (peroxidase-antiperoxidase) with the monoclonal antibody MIB-1. Epithelial expression of Ki-67 was classified as being absent, basal, and suprabasal. The epithelium was normal in 19 cases, hyperplastic in 38 cases, and dysplastic in 37 cases. The dysplasia was slight in 20 cases, moderate in 12 cases, and severe in 5 cases. The results of the expression of Ki-67 were in normal epithelium, basal expression 9 cases, absent 10 cases; in hyperplastic epithelium, basal expression 18 cases, absent 20 cases; in dysplastic epithelium, basal and suprabasal expression (always jointly) 27 cases, absent 10 cases; all the severe and moderate dysplasia cases expressed suprabasal Ki-67. A significant association was observed between the presence (p <.0001) and severity (p <.007) of the dysplasia and the suprabasal expression of Ki-67. Copyright 2000 John Wiley & Sons, Inc.