Immunosuppression for organ transplantation is a modern concept. The earliest reports of organ replacement have their roots in mythology and human fantasy. The primacy of overcoming the immunologic barrier for successful transplantation of organs has been influenced by geopolitical conflict, unorthodox ideas, application of knowledge across medical disciplines, and serendipity. The earliest form of chemical immunosuppression had its origin in chemical gas in warfare. Further developments in immunology, cancer therapy and biochemistry helped shape the intellectual basis for the introduction of chemical immunosuppression.