Acute rejection is characterized by renal ischaemia which in turn is a triggering factor of EPO synthesis. This fact justified our present studies which aimed to assess the influence of acute rejection (AR) on plasma EPO level in KTP. A total of 17 KTP were examined some days before AR (I), at the onset of AR (II), immediately (III) and some days after (IV) discontinued therapy of AR episodes by methylprednisolone. The control group consisted of 16 healthy subjects. KTP 2-3 weeks after renal transplantation showed relative EPO deficiency both during efficient excretory function and rejection episodes. At acute graft rejection episodes a marked increase of plasma EPO level was found. Results presented in this study suggest absence of the physiological relationship between EPO secretion and erythropoiesis 2-3 weeks after transplantation.