Two cases of spontaneous rupture of the kidney are reported and the literature is reviewed. The clinical and pathological features of this uncommon disease and its treatment are discussed. In the first case the cause of retroperitoneal bleeding was a renal carcinoma, while in the second it was the result of renal metastases from gestational trophoblastic disease. The most common symptoms are an acute onset of flank or abdominal pain, macroscopic hematuria and a drop in the hemoglobin level. Resistance or a mass can be palpated. Ultrasound and radiological examinations allow visualization of a tumor or hematoma and mostly reveal the etiology of hemorrhage. An exploratory operation is necessary for diagnosis, and primary nephrectomy should be seriously considered.