A review of oral leukoplakia, based on data from the literature and experience with 84 patients is presented. The leukoplakic lesions of 3 patients developed malignant transformation within an average period of 5 years. All three patients were elderly women with idiopathic leukoplakia, in two cases of the homogeneous and in one case of the non-homogeneous type. The initial biopsy of the former two patients showed only hyperorthokeratosis without epithelial dysplasia. In the first biopsy of the third patient epithelial dysplasia was recorded. One of the patients finally died of widespread metastases. The other two have been treated surgically and are still alive.