Optimal therapeutic management in transplantation delivers the least amount of immunosuppressive drugs required to avoid graft rejection since overtreatment could lead to undesirable side effects like malignancies and infections. The development of new immunosuppressive drugs reflects the progress in understanding the molecular mechanism involved in allograft rejection. Each type of transplant has its own type of evolving immunosuppressive strategies. This review presents new aspects of antigen recognition by T lymphocytes, general mechanisms of action and deleterious effects of immunosuppressive drugs. Clinical results obtained in the main organ transplantations are also discussed.