This volume offers an analysis of the scale and nature of the immunological issues facing regenerative medicine, drawing on the expertise of laboratories around the world who have taken up the challenge of applying their expertise in immunology to the vagaries of stem cell biology. In Part I, we explore the extent to which the principles of allograft rejection, learned over several decades from our experiences of whole organ transplantation, apply within the unique context of cell replacement therapy. Part II discusses various innovative ways of addressing the issues of immunogenicity, while, in Part III, we focus exclusively on the induction of immunological tolerance through a variety of novel approaches. It is our hope that this systematic analysis of the current state of the field will galvanise efforts to solve an issue which has so far remained intractable.