Purpose : To correlate the CT findings of renal cell carcinomas with nuclear grading in histopathology.Materials and Methods : Preoperative CT scans and pathologic nuclear grading of 60 surgically resected renal cellcarcinomas in 55 patients were retrospectively and independently reviewed. Results : As nuclear grade increased,renal cell carcinomas were more likely to be of higher stage (92% of nuclear grade III renal cell carcinomas wasof stage III, all Grade IV tumors were of stage IIIb or higher) and greater size (84% of grade III tumors and 100%of grade IV tumors > 5cm in size) at presentation, and appeared more heterogeneous (84% of grade III tumors and88% of grade IV tumors showed moderate or severe heterogeneity) and less well marginated (84% of grade III tumorsand 100% of grade IV tumors had irregular or imperceptible margins). Conclusion : Small well-marginatedhomogeneous renal cell carcinomas were either nuclear grade I or II, and were distinguishable from the moreaggressive nuclear grade III or IV lesions, which generally displayed irregular margins and greater inhomogeneity.