A simple technique is described for the autoimplantation of splenic tissue in the peritoneal cavity of rats. The effect of splenic implants on irradiated splenectomised rats was investigated, by following the evolution of the implants both microscopically and macroscopically. The effect on haemopoiesis was also observed. The dose of irradiation given was sublethal, do not think it necessary to put in, and non lethal.