The role of nephron-sparing surgery for renal cell carcinoma is well established in patients with an anatomical or functional solitary kidney (imperative indication) in which a radical nephrectomy would render the patient anephric with subsequent need for hemodialysis. This also encompasses patients with a unilateral renal cell carcinoma and a functioning contralateral kidney when the opposite renal unit is affected by a disease that might threaten its future function, such as renal artery stenosis, chronic pyelonephritis, stone disease or systemic conditions such as diabetes. A functioning renal remant of at least 20% of normal renal parenchyma seems to be necessary to avoid end-stage renal failure in these patients [16]. There have been several reports in the literature of excellent 5-year cancer-specific survival rates of over 80% in such circumstances [12, 15]. These results were confirmed in our institution, with a 5-year cancer-specific survival rate of 83% in over 70 patients with an imperative indication for nephron-sparing surgery. Thereby the prognosis was significantly influenced by the local tumor stage and the grade of malignancy. These data support the efficacy of nephron-sparing surgery in this clinical situation.