Marek’s disease is a form of cancer of poultry caused by an important herpesvirus (MDV). It continues to be a threat to poultry health and welfare and worldwide losses are estimated to be US$ 1 billion annually. Marek's Disease provides a timely review of the problems of Marek's disease with descriptions of the complex viral life cycle, how MDV targets different types of white blood cells, and details of the virus structure, its genes and proteins.