The process of transplantation of tissues and organs, as a highly specialized treatment method, has a unique place in the field of medical science and practice. On occasion of the 40 anniversary of the first renal transplantation in adult in Bulgaria, the developments in this area are reviewed chronologically. The initial experiments on test animals, as well as the first renal transplantation in adult are described in details. For the abovementioned period 435 renal transplantations have been performed in UMHAT "Alexandrovska", 231 (53.2%) form living kidney donor and 204 (46.9%)--from cadaveric renal donors. The benefits of the existing organization of transplantation in UMHAT "Alexandrovska" are outlined, as well as the problems preventing the transplantation process to achieve even wider usage as a method for treatment of end-stage organ diseases.