Nine patients with thoraco-abdominal aortic dysplasia with and without renal artery involvement are reported. All were treated surgically with no early or late mortality. They have been followed up for from 2 to 12 years. The majority of the patients, at the time of writing, are symptomless and normotensive. Hypertension, especially in young people, was the dominant presentation. This is often associated with arterial insufficiency of the lower extremities. Arteriography is essential and provides the correct diagnosis and suggests the appropriate surgical treatment. The aetiology is unknown but evidence points to a congenital process aggravated by secondary changes. Histological studies show a dysplastic process affecting mainly the media and intima.