An account is given of the basic theory underlying the use of ultrasounds in the diagnosis of dilatation of the abdominal aorta, and its practical value. The limitations of physical examination and vacuum radiography, and the contraindications, inconveniences and risks associated with aortography are points in favour of echography. The salient features of its application in suspected aneurysm are described with reference to 12 clinical cases. This simple and harmless examination offers a reliable and non-invasive means of detecting the presence and determining the size of such aneurysms with safety and certainty.