Renal cell carcinoma is a tumor, the prognosis and behavior of which remain poorly understood. Proliferating cell nuclear antigen levels have been shown to act as an independent prognostic variable in a variety of malignancies. Proliferating cell nuclear antigen was evaluated in 59 cases of renal cell carcinoma, and the results were correlated with existing clinicopathological variables and survival. Proliferating cell nuclear antigen index (percentage of tumor cells positive for proliferating cell nuclear antigen) did not correlate with stage, grade or ploidy. To assess survival, tumors with proliferating cell nuclear antigen indexes of greater than and less than 60% were compared. The 24 patients with a high index (greater than 60%) had a significantly worse survival than did 35 with a low index (less than 60%, p < 0.001). Therefore, the prognostic potential of proliferating cell nuclear antigen in renal cell carcinoma is promising and may be of clinical value in the management of patients with renal cell carcinoma.