The proliferative activity of 21 cases of renal cell carcinoma has been investigated by means of monoclonal antibody Ki-67 and Nucleolar Organizer Regions (AgNORs) analysis. The correlation between AgNOR counts and Ki-67 scores was only slightly significant (r = 0.53, r2 = 0.28) as determined by linear regression. Positive correlation was found between Ki-67 scores and tumour histologic grade. However, no correlation was observed between Ki-67 scores and tumour pathologic stage and between AgNOR counts and tumour histologic grade and/or pathologic stage. The results suggest that AgNOR counts cannot replace Ki-67 scores in evaluating the proliferative activity of renal cell carcinoma and that such activity and both histologic grade and pathologic stage seem to be independent parametres.