Oral cancer as become one of the sixth most common cancer worldwide and also represents about 5.5% of all malignancies. In the Western world it is less common, but the incidence is increasing and the mortality rate has not improved for decades. Although most oral cancers probably arise in clinically normal mucosa some are preceded by a precancerous lesion which indicates an increased risk of cancer development at a particular site. The histopathologist's role is to recognize pathological features which indicate high risk and to provide prognostic information from examination of excised tumours. The most common precancerous lesion is a white patch on the oral mucosa referred to as a leukoplakia. These show variable clinical features ranging from relatively innocuous flat white plaques to verruciform or red and white speckled lesions. A proportion of' precancerous lesions show features of cytological atypia which are usually graded as mild, moderate or severe. The degree of epithelial dysplasia is a useful guide for the management of such lesions. In this book we cover relevant anatomy, biology, diagnosis and latest management strategies for pre-cancerous conditions that affect the oral mucosa. The respective chapters are written by expert contributors from around the world, lending the book a global perspective and making it an essential guide for all those involved in the management of pre-malignant lesions arising in this challenging anatomical region.