Two hundred thirty-five cases of histologically proved renal cell carcinoma (1976-1987) were reviewed to determine the impact of incidental tumor detection on the natural history of this cancer. One hundred sixty-eight patients (71.5%) presented with clinical signs and/or symptoms of renal pathology. Of these, 25 (18%) were investigated without consideration of renal cell carcinoma in the differential diagnosis. Sixty-seven cases (28.5%) were diagnosed as an incidental finding on diagnostic imaging for extrarenal symptomatology. Approximately 30 percent of patients were found to have metastatic disease on initial presentation regardless of incidental, or suspected discovery of these tumors. Stages A and B tumors were encountered with equal frequency in patient groups with both suspected and incidental diagnosis. Intravenous pyelography was the diagnostic modality used to detect the diagnosis in 83 percent of cases. While incidental detection of renal cell carcinoma has become more frequent than in previous years, it appears to have impacted minimally on the discovery of earlier stage tumors than those with presenting clinical symptoms. In contrast to prior reports, our data show that the natural history of renal cell carcinoma is not significantly altered by the incidental detection of tumor.