Although cases of autosomal dominant polycystic kidney disease (ADPKD) associated with abdominal aortic aneurysm have been repeatedly reported in the literature, no systematic studies of the aortas of these patients have been performed. In the study presented here, a sonographic study of the abdominal aorta in 139 ADPKD patients and in 149 healthy family members was carried out. For both groups, an increase in aortic diameter related to age and sex, (being wider in men than women) was found. In ADPKD patients, neither a wider aortic diameter nor a higher prevalence of abdominal aortic aneurysms could be found in any age group. It was concluded that, although these patients are prone to develop aortic aneurysms because of hypertension and associated connective tissue disorders, the presence of abdominal aortic aneurysms should be questioned as a frequent feature of ADPKD.