In a prospective study during the period January-May 1992, 362 consecutive out-patients above 65 years of age, attending the pulmonary department for chronic obstructive airways disease (COPD), were ultrasonographically screened for an aneurysm of the abdominal aorta (AAA). Data from pulmonary function tests together with history of cardiac disease, diabetes mellitus, hypertension, hypercholesterolaemia, peripheral arterial obstructive disease, smoking and corticosteroid medication were collected. 30/282 men and 6/80 women with COPD had an AAA > or = 30 mm in diameter, which equals a prevalence of 9.9% (95% confidence limits: 6.8-13.0%). COPD patients with severe emphysema, having a decreased forced expiratory volume/vital capacity ratio (FEV/VC) of < 55%, have a significantly higher prevalence of aortic dilatation or AAA compared to COPD patients with mild or moderate decreased FEV/VC (chi-squared test: p < 0.05, alpha = 0.05). In the group of patients with AAA, significantly more smokers were seen compared to the group with normal and dilated aortas (chi-squared test: p < 0.05).