Congenital anomalies of the inferior vena cava are a relatively rare pathology, usually with an asymptomatic iter. They are usually diagnosed by chance during surgery on the aorta or retroperitoneal structures. From bioptic material their incidence is estimated to be 2-3% and the percentage of intraoperative findings varies in different series between 0.2 and 0.6%. Of the various kinds of anomaly, caval duplication and a left-positioned vena cava are those most commonly found. The recent report of a case of a malpositioned vena cava and iliac veins prompted us to re-examine the literature and revise our series of cases.