PURPOSE: To evaluate the CT appearance of renal cell carcinoma and to correlate it with nuclear grading andcell type. MATERIALS AND METHODS: The size, outer margin and heterogeneity of inner texture of renal cell carcinomas in 86 patients were evaluated on CT scan and were correlated with nuclear grade and cell type. RESULTS: Tumors less than 5cm were of low grade in 28 of 31 patients, while those larger than 5cm were of low grade in 28 of 55 patients. The lesions which showed no or round protrusion with a sharp margin were of low grade in 26 of 28 patients, while those which showed an undulated or indistinct margin were of low grade in 30 of 58 patients. Lesions which showed a homogeneous solid appearance, focal low densities, or mostly cystic changes were of low grade in 23 of 26 patients, while those which showed multiple or confluent low densites were low grade in 33 of 60 patients. There was a significant difference in the distribution of nuclear grading between the groups. Differences in CT apperance according to cell type were not found. CONCLUSION: Differences in less than 5cm showing no or round protrusion with a sharp margin, homogeneous inner texture with solid appearance, and heterogeneous inner texture with cystic appearance or focal low densities on CT scan were thought to be the findings suggesting low nuclear grading.