It has become a tradition to commence important meetings of this society with reminiscence and nostalgia. Bone marrow transplantation, which has a history of only 30 to 40 years, permits this process, since some of the early investigators are still with us. For example, over the past 15 years, we have had three symposia in honor of Egon Lorenz. As we all know, the team of Lorenz, Uphoff and Congdon was involved in the first successful transplantation of syngeneic and allogeneic bone marrow into irradiated mice (1). Subsequently, these investigators theorized that a humoral factor probably was responsible for the radiation protection, as documented by the injection of rat bone marrow into irradiated mice (2).