Renal cell carcinoma of transplanted kidneys is rare. We report three such cases among 1,250 kidney grafts that were performed or followed from 1968 to 2002. A strategy to diagnose these lesions is needed because of their rarity, late detection, and therapeutic repercussions. At the least, the strategy should include annual ultrasonography of the graft throughout its lifespan. Because the risk of tumor development in another organ from the same donor is not negligible, a national registry should be established to rapidly alert graft recipients with the same donor and other transplantation centers about the risk of graft tumors.