Main focus of the new book will be the description and discussion of rat and mouse models for organ transplantation. Various microsurgical techniques will be presented which allow transplantation of functional organs in syngeneic systems. In particular, the extremely difficult methods necessary for organ transplantation in mice will be presented and evaluated. Besides these practical aspects the book will also cover the theoretical sides of organ transplantation like the immunobiology of allotransplantation. Special emphasis will be given to the resurgent field of xenotransplantation. The results from xenograft models developed in the recent years using rats or mice will be reviewed and their impact on future human xenotransplantation will be discussed.