Our treatment of acute renal cellular rejection in patients on ciclosporin (cyclosporin A) involves the almost complete elimination of T cells (according to individual T cell monitoring in peripheral blood) through antithymocyte globulin (ATG) therapy. We present here the results of treatment of 44 histologically or cytologically proven acute rejection episodes in 33 of 62 consecutive renal transplantation patients. ATG therapy resulted in a 95.5% success rate when duration and dosage were individually adjusted according to T cell elimination in peripheral blood. Only two grafts were lost, both because of vascular occlusions. In neither case could it be clarified whether the loss was due to primary vascular lesions or the result of severe rejection or side effects of ATG. Our data show that the elimination of primed T cells with ATG permits the use of ciclosporin even in the presence of an established immune response.