Several immunological factors affect the outcome of human kidney transplants. HLA-A, -B and -DR matching improves kidney graft survival rate, especially matching for HLA-DR antigens. The beneficial effect of pretransplant blood transfusion has been confirmed although the mechanisms of the beneficial effect are not clear. Donor specific transfusion prior to living related donor kidney transplantation improve graft survival but some 30% of potential recipients become sensitized to the donor during the transfusion process. Major improvements in the results of organ transplantation have been achieved during the past few years with the use of new immunosuppressive agents, namely cyclosporin and monoclonal antibodies reacting with T lymphocytes. Both agents act selectively on T lymphocytes. However, nephrotoxicity of cyclosporin may limit its use.