The definition, nature and frequency of oral leukoplakia. Objectives.- I. Results of clinical follow-up studies in oral leukoplakia.- Malignant trasformation rate.- Age and Sex distribution.- Site of leukoplakia and carcinoma.- Correlation between the clinical type and malignant transformation of oral leukoplakia.- Latency period.- II. The role of etiological factors.- The etiological importance of smoking habits.- Cytological investigations.- Histological examinations.- The etiological importance of mechanical factors.- The etiological importance of differences in electrical potential.- The role of inflammatory and atrophic changes of the oral mucous membrane in the pathogenesis of leukoplakia.- Migratory glossitis.- Lesions of the tongue in association with anaemia.- Median rhomboid glossitis.- III. Transformations in the clinical type of leukoplakia during longitudinal studies.- IV. Comparative study of the clinical types and histological characteristics of oral leukoplakia.- Epithelial changes.- Connective tissue changes.- Comparative analysis of non-dysplastic cases.- Incidence of epithelial dysplasia and longitudinal study of leukoplakias with dysplasia.- V. Cytological studies in oral leukoplakia.- Studies of the keratinization pattern in oral leukoplakia.- The value of cytodiagnostics in the detection of cancer development from oral leukoplakia.- VI. Electron microscopic studies of oral leukoplakias.- Transmission electron microscopic (TEM) studies.- Simple leukoplakia.- Verrucous leukoplakia.- Erosive leukoplakia.- Morphometric (stereological) investigations.- General morphometric features of leukoplakic and normal epithelium.- Composition of the epithelial tissue.- Structural density gradients of cytoplasmic organelles.- Scanning electron microscopic (SEM) examinations.- VII. Oral white lesions other than leukoplakia.- Clinical (longitudinal) studies on patients with oral lichen planus.- Simultaneous occurrence of leukoplakia and oral lichen.- InvestigatlÓ,