From January 1956 to March 1987, 100 patients underwent a conservative (parenchyma-sparing) operation as curative treatment for renal cell carcinoma at our clinic. This series includes 56 patients with bilateral (28 synchronous and 28 asynchronous) and 44 with unilateral renal cell carcinoma; in the latter category the contralateral kidney was either absent or nonfunctioning (17 patients), functionally impaired (17), involved with a benign disease process (6) or normal (4). The pathological tumor stage was I in 75 patients, II in 9, III in 10 and IV in 6. A nephron-sparing operation was performed in situ in 86 patients and ex vivo in 14. Postoperatively, 93 patients experienced immediate function of the operated kidney, while 7 required dialysis (4 temporary and 3 permanent). The incidence of dialysis was greater after ex vivo than in situ surgery (p equals 0.0005). The mean postoperative serum creatinine level in 97 patients with renal function was 1.7 mg. per dl. (range 0.9 to 4.6 mg. per dl.). The over-all actuarial 5-year patient survival rate in this series is 67 per cent including death of any cause and 84 per cent including only deaths of renal cell carcinoma. Survival was improved in patients with stage I renal cell carcinoma (p less than 0.05). Survival also was improved in patients with unilateral renal cell carcinoma (p less than 0.05) and fewer patients in this category had recurrent disease postoperatively (p less than 0.0005). Nine patients (9 per cent) had local tumor recurrence postoperatively and 5 of these were rendered free of tumor by secondary surgical excision. Conservative surgery provides effective therapy for patients with localized renal cell carcinoma in whom preservation of renal function is a relevant clinical consideration.