Between 1969Between und 1989 conservative surgery for kidney tumors was performed in 123 patients. In 49 patients there was an imperative indication for a parenchyma-sparing operation because nephrectomy would have made dialysis obligatory. Thirty-five of these 49 patients show no signs of tumor progression after a mean follow-up of 4.5 years. Known metastases were present in 3 of 6 patients who died as a result of their tumors. In two patients there was a recurrence after 1 and 5 years, respectively, requiring a second organ-preserving operation. In one further patient we suspect that multiple small tumor lesions may be present 2 years after the first operation. In 74 patients with a healthy contralateral kidney the tumor was enucleated by choice (elective indication). Sixty-eight of these 74 patients show no signs of tumor progression after a mean follow-up period of 3.3 years. One patient died from tumor metastases. Two patients had tumor recurrence, requiring nephrectomy and enucleation, respectively. Fifty-seven enucleated tumors were available for image analysis DNA cytometry. Only the two patients with a hypertriploid tumor died from their cancer.Until now radical nephrectomy has been regarded as standard therapy for non-metastasized renal cell carcinoma [15,18,21]. This operation has been accepted because of its theorized advantage of more complete resection. A parenchyma-sparing operation has only been performed on patients in whom radical nephrectomy would result in renal failure requiring hemodialysis (imperative indication), such as those with a single kidney, bilateral tumors, dysfunctional contralateral kidney or chronic renal failure. However, the widely used partial nephrectomy in these instances may result, in certain cases, in insufficient residual renal parenchyma [14]. Simple enucleation of the tumor, together with a small surrounding margin of normal renal tissue, is an alternative technique to this * To whom correspondence should be addressed approach. The surprisingly good prognosis of patients, which were treated by enucleation in the imperative group [1], encouraged us over the past 9 years to perform parenchyma-sparing operations also on patients with small peripheral tumors and normal contralateral kidneys (elective indication). In addition, these small and mostly asymptomatic kidney tumors, which only a few years ago were rarely diagnosed, are being detected more frequently by ultrasound. Thus, the incidence of asymptomatic renal tumors increased from 10% in 1978 to 70°70 in 1989, while the classic symptoms of flank pain, hematuria and palpable mass were found in less than 10% of the cases, Here we present the operative technique, complications, patient outcome and preliminary results of image analysis DNA cytometry. Between 1969 and, conservative surgery of kidney tumors was performed in 123 patients. Conservative surgery was imperative for 49 of the patients (18 female, 31 male) aged 38 to 77 years (average age 59 years). A total of 23 patients had metachronous or synchronous bila...