The authors of this new fourth edition recognise that nomenclature for cysts and neoplasms of the jaws is dynamic, as demonstrated by the evolving schemes based on previously unrecognised microscopic, clinical, radiographic, and therapeutic features. This edition is not an attempt to promote one nomenclature scheme versus another, but simply to present the best information available for each lesion discussed using the most current World Health Organization classification system. While this edition continues in the American Registry of Pathology tradition of providing the most current diagnostic information available for the practising pathologist, in some cases surgeons will consult with pathologists regarding therapeutic management, hence information about peer-reviewed treatment protocols for many tumours and cysts is included in each section. This edition promises to be a quality resource for pathologists, surgeons, and dentists alike for many years.