The only effective treatment of an aortocaval fistula is the surgical closure of the fistula opening with insertion of an aortic prosthesis to restore the arterial continuity. The diagnosis of this distinct but infrequent clinical entity is often missed because of lack of suspicion. Proper preoperative evaluation facilitates the choice of surgical approach and reduces the morbidity. Three patients are presented with an aortocaval fistula: two with spontaneous rupture of an atherosclerotic abdominal aneurysm into the inferior vena cava and one with a traumatic fistula following intervertebral disk surgery 33 years before. All three patients suffered from pain in the abdomen and back, a palpable pulsatile abdominal mass and an audible continuous harsh bruit. Cardiac failure was present in two of them. Successful surgical closure could be accomplished in two patients although the perioperative course was complicated by ventricular arrhythmia, profuse blood loss and an inferior vena cava syndrome. One patient with a spontaneous aortocaval fistula passed away due to intraoperative exsanguination.