Both pre- and postnephrectomy levels of serum creatinine were measured in 52 consecutive patients who underwent radical nephrectomy for localized renal cell carcinoma between 1971 and 1976. At the time of follow-up, 17 patients were alive and 35 had died, 14 of renal cell carcinoma and 21 of other causes. Follow-up lasted a minimum of 115.5 months (mean 151.1 months, median 141.1, range 115.5-211.3 months) for 16 of the 17 patients who were alive. In this group only 2 patients had elevations in the serum creatinine level above 1.6 mg/dL-1.9 mg/dL and 2.4 mg/dL, respectively. The patient whose value was 2.4 mg/dL was a diabetic who required insulin. No serious renal failure, renal disease, or tumors in the contralateral kidney occurred among the total group of 52 patients. These data indicate that renal function remains adequate in patients who have a normal contralateral kidney and are treated by radical nephrectomy.