Two cases of aortocaval fistula are described in patients with an otherwise asymptomatic abdominal aortic aneurysm. Both presented because of cardiac symptoms, one with chest pain and acute heart failure and electrocardiogram signs of acute coronary ischaemia, the other with a long history of chronic cardiac failure resistant to therapy. In the first case the fistula was proven by means of a CAT scan. Positive proof of a fistula or leakage is important because asymptomatic aneurysms should not be operated on in cardiac compromised patients. On the other hand, if an aortocaval fistula is present, operation is necessary to prevent fatal cardiac failure.