Experimental and clinical evidence presented in this book illustrates that antibodies expressing different specificities can be very effective in preventing or reversing established transplant rejection. Moreover, the data leads us to hope that the use of these new therapeutic agents may allow the induction of specific tolerance to transplant alloantigens which is the only means to avoid the major risks of sustained immunosuppression, namely an increased susceptibility to infection and tumor development. In this volume the editors combine contributions dealing with very practical aspects of the clinical use of monoclonal antibodies with a more general discussion on the developments one may foresee in the near future.