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 cell carcinomas 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 was of stage Ill, 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 and 88% of grade IV tumors showed moderate or severe heterogeneity) and less well marginated(84% of grade Ill tumors and 100% of grade IV tumors had irregular or imperceptible margins). CONCLUSION: Small well-marginated homogeneous renal cell carcinomas were either nuclear grade I or II, and were distinguishable from the more aggressive nuclear grade III or IV lesions, which generally displayed irregular margins and greater inhomogeneity.