In the last 8 years 15 patients with malignant neoplasms in functionally solitary kidneys underwent in situ excision of the tumor with preservation of renal parenchyma. Of 10 patients with renal cell carcinoma 8 underwent partial nephrectomy, 1 had a central wedge resection and 1 had enucleation of 3 tumors. After followup of 6 months to 4.7 years 6 patients are free of disease. One patient died of metastatic cancer and 1 of cardiovascular disease. Of 5 patients with transitional cell carcinoma of the kidney (including 2 with parenchymal invasion) 2 underwent partial nephrectomy and 3 underwent extensive resection of renal pelvic lesions. After followup of 6 months to 7 years 2 patients are alive, 2 died of metastatic disease and 1 died of metastatic bladder carcinoma. Only 1 of the 5 patients had locally recurrent tumor. These data demonstrate the efficacy of in situ management of renal tumors in selected patients with solitary kidneys or compromised renal function.