We retrospectively examined the cases of renal tumors experienced between 1993 and 2002 to evaluate the rates of incidence and preoperative identification by imaging techniques, mainly CT, of retroperitoneal venous abnormalities. Among a total of 178 renal cell carcinomas and 13 renal benign tumors, the incidence of multiplicity of renal veins was 5.3%, restricted to operatively confirmed cases (9 out of 170 cases). None of these multiplicities could be detected by preoperative radiological examinations. Other major venous abnormalities included duplications of inferior vena cava and retroaortic left renal vein and spontaneous splenorenal shunt which were all correctly diagnosed preoperatively. The incidence of these abnormalities was 0.52% (1 out of 191 cases for each). A retroperitoneal venous anomaly is common, but urologists must have sufficient knowledge about acquired retroperitoneal venous abnormalities, which seem rather uncommon, to be prepared for the potential hazards which may occur during urological operations.