The contrast-enhanced preoperative computed tomographic (CT) scans and microscopic slides of 94 patients with 100 surgically resected renal cell carcinomas (RCCs) were retrospectively and independently reviewed in order to correlate the CT imaging findings of RCC with nuclear grading. As nuclear grade increased, RCCs were more likely to be of higher stage and greater size at presentation, and appeared more heterogeneous and less marginated. Of the features analyzed, tumor margination most closely correlated with nuclear grade. Overlap in the CT appearance of individual tumors limited the potential of CT to differentiate RCCs of varying grade. Small, well-marginated, homogeneous tumors, however, were either grade I or II, and were distinguishable from the more aggressive grade III lesions, which generally displayed irregular margins and greater inhomogeneity.