Oncocytomas are tumors characterized by cells with an eosinophilic cytoplasm. Renal oncocytomas were described in 1942. Among 46 consecutive patients operated on for renal tumors, oncocytomas were found in 4 (8.7%). In spite of a supposedly benign nature, renal oncocytoma cannot be adequately differentiated from renal adenocarcinoma by imaging techniques. Therefore, we recommend radical surgery as the treatment of choice in these patients.