to study incidence, clinical presentation and problems in management of aortocaval fistula in our series.retrospective study.during a seven-year period, 112 patients operated on for abdominal aortic aneurysm, including four patients with aortocaval fistula.standard repair of aortocaval fistula from inside the aneurysmal sac was the preferred operative technique.the incidence of aortocaval fistula was 3.6%. Three cases were found incidentally during emergency surgery for ruptured aneurysms; the fourth case was an isolated aortocaval fistula associated with inferior vena cava thrombosis, diagnosed preoperatively by angiography. In this case, inferior vena cava ligation instead of standard aortocaval repair was performed.Aortocaval fistulas, although rare, should be kept in mind, because clinical diagnosis is often difficult. Furthermore, unsuspected problems during repair may necessitate appropriate change in operative technique.