Renal cell carcinoma (RCC) occurring in renal allografts after cadaveric kidney transplantation has rarely been observed. RCC accounts for 2.3% of all malignancies in the general population, but up to 4.8% of malignancies in renal transplant recipients. Most have been reported in the patient's own diseased kidneys, whereas RCC in the renal allograft occur in only 10%. Here, we describe an organ-preserving surgical technique of a malignant renal tumor in a kidney allograft using a harmonic scalpel (Ultracision) for tumor enucleation. Furthermore we demonstrate by DNA microsatellite analysis the tumor's genetic origin as donor related. Collectively, we suggest that patients with a well defined low grade RCC in the kidney allograft and altogether low malignancy and good allograft function should only undergo an organ-preserving procedure and short-term postoperative screening.