PURPOSE: To describe the spiral CT findings of CRCC and to correlate these with the pathologic features, nuclear grading, tumor staging, and prognosis. MATERIALS AND METHODS: We encountered eleven cases of CRCC among 167 cases of histopathologically proven RCC, retrospectively evaluating the spiral CT findings of CRCC including tumor size, internal texture, attenuation, margin, and the involvement of veins or lymph nodes. In addition, the CT findings were correlated with the pathologic features, Fuhrman's nuclear grade, Robson's staging, and the prognosis. Between 27 and 80 (mean, 49.6) months later, the follow-up CT scans of tea patients were examined for tumor recurrence. RESULTS: All tumors, which ranged in size from 2.5 to 15 (mean, 7.7) cm, were solid and well demarcated from renal parenchyma. Pre-contrast CT scans showed that their attenuation was equal to (n=1) or slightly lower (n=10) than that of renal parenchyma, and on early and delayed phase post-contrast enhanced scans, attenuation was low in all cases. In three, focal areas in which attenuation was lower than in the rest of the tumor were observed; histopathologically, these represented hyalinization. There was neither venous nor lymph node involvement, and no distant metastasis. Histopathologic examination demonstrated cystic change (n=1), hemorrhage or necrosis (n=5), complete encapsulation (n=3) and perirenal fat infiltration (n=3). Nuclear grading was II (n=6) or III (n=5), and tumor staging was I (n=8) or II (n=3). Among the five cases in which the nuclear grade was III, three were stage I and two were stage II. Follow-up scans showed no evidence of tumor recurrence, and all patients survived. CONCLUSION: Pre-, early- and late-phase post-contrast enhonced spiral CT scans showed that the attenuation of a CRCC was lower than that of renal parenchyma. Even where the nuclear grade was higher, a well-demarcated soild mass was observed, the tumor stage was lower and the prognosis better.