A total of 33 renal venograms were reviewed to determine the incidence of radiographically demonstrable valves. Valves were identified in five of 22 left renal venograms and two of 11 right renal venograms. On the right side in both patients the valve was located at the junction of the renal vein with the inferior vena cava. On the left, valves were located in the main renal vein proximal or distal to the gonadal vein and in one patient in a segmental upper pole tributary. These valves are significant because of the technical difficulties they can create during renal venography and their possible usefulness in selecting the site of anastomosis in patients undergoing distal splenorenal shunts.