Gross hematuria with abdominal pain may be caused by entrapment of the left renal vein between the aorta and the superior mesenteric artery. In the urinary sediment the erythrocytes are normally shaped, making a renal parenchymatous cause unlikely. Ultrasonography shows a decrease of the diameter of the left renal vein of more than 50%, in every position of the patient. Cytoscopy à chaud reveals hematuria pouring out only from the left ureter. In this paper four patients with this syndrome are presented.