We report the largest renal oncocytoma excised at the initial presentation and the second largest renal oncocytoma in published reports. Despite a tendency for renal oncocytomas to be relatively small and asymptomatic compared with renal cell carcinomas, these lesions cannot be reliably differentiated preoperatively. The variable nature of presentation and overlap of radiographic characteristics between these lesions complicates their clinical differentiation. The present case illustrates the difficulty in the preoperative diagnosis of even very large, enhancing renal masses and reinforces the inclusion of renal oncocytoma in the differential diagnosis of these lesions.