Renal oncocytoma is an epithelial tumor of the kidney, which is composed of oncocytes and appears in the distal tubules or collecting ducts of the renal parenchyma. According to different authors, oncocytomas comprise 3 to 7% of all primary renal tumors. Until recently it has been held that highly differentiated oncocytoma is always a benign tumor. However, this opinion has turned out to be erroneous, since several cases of the aggressive course of this tumor are described, the mass can metastasize or infiltrate the surrounding tissues during extrarenal growth. Vascular invasion can rarely occur. During radiological investigations, the presence of a stellate scar in the center of the tumor is considered to be a relatively pathognomonic sign for oncocytoma; however, it should be remembered that a scar can also occur in adenoma, clear-cell, and chromophobe renal-cell carcinoma. At the same time, no scar may be detected in small (<4 cm) oncocytomas. Thus, it is difficult to preoperatively diagnose renal oncocytoma. Taking into account also the conventional attitude to oncocytoma as a benign mass and the new evidence that its course may be malignant, it is advisable to perform surgical treatment if renal oncocytoma is suspected. The volume of intervention should be determined according to the size and site of the tumor. The paper describes a clinical case of a 64-year-old male patient with renal oncocytoma (informed consent for publication of data has been obtained from the patient). The radiological diagnostic data for the mass were similar to those for kidney cancer, which could not differentiate the tumor preoperatively. The insignificant sizes of the tumor and the extra-organ location of its most part allowed kidney resection. No disease recurrence was shown at the 1-year follow-up examination.