Spontaneous retroperitoneal bleeding is a rare clinical feature of renal cell carcinoma. A 67-year old man was sent to our emergency unit because of a sudden attack of right flank pain. An abdominal mass, ever and leukocytosis were noted. Abdominal CT scan revealed a heterogenic upper pole mass and hyperdense perinephric hematoma. Arteriography showed an avascular right renal mass. Radical nephrectomy and postoperative radiotherapy were performed. No local recurrence was detected after nine months of follow-up. The diagnosis and management are discussed.