A screening ultrasonography was performed in 325 first degree relatives aged 50 years or above of patients who had been operated on for an aneurysm and 281 control persons who had no family history of aneurysms . Three brothers of the patients had already been operated on because of an aneurysm. 11/101 brothers (10.9%) had an aneurysm measuring at least 30 mm in diameter. In the control group 2 men and 2 women had an aneurysm. A dilated abdominal aorta (20 - 29 mm) was detected in 30 first-degree relatives and none of the control persons.