Biopsies from 13 oral leukoplakias and from normal tissue specimens in the contralateral region of each patient were examined microradiographically and lipid-histochemically using freeze-sectioned and freeze-dried sections. The investigation showed that an epithelial zone of cell layers with different degrees of keratinization and varying dry mass concentrations occurred in oral leukoplakias. A concentrated localization of phospholipids, free fatty acids and cholesterols was found in the zones with a high dry mass content and, consequently, high keratin content, while a negative lipid reaction was obtained in the zones where the dry mass concentration was low.