The use of animals as a source of cells, tissues, and organs for transplantation has been of increasing interest in recent years. Transplantation of animal tissues into human patients is occurring now at various centers and the possibility of organ xenotransplants is widely discussed. This volume presents a balanced review of recent progress in understanding the immunologic aspects of xenotransplantation and zoonotic risks. It addresses how the application of various immunosuppressive modalities might compromise the immunological competence of recipients and examines the relevant issues relating to zoonotic disease. This is the first book to deal with the issues of host defense and zoonosis in xenotransplantation and points to the critical issues that must be addressed to make the process safe from the perspective of the patient and society as well as critical questions yet to be answered. Valuable reading for physicians, scientists, and those engaged in the development of policies for the field of xenotransplantation, especially with regard to zoonosis.