Aortosonography for the measurement of the lumen and wall thickness of the abdominal aorta is of value in the detection and study of abdominal aortic aneurysms. Anteroposterior measurements may be supplemented by lateral determinations to provide more exact assessment of the aorta. A dilated descending thoracic aorta, reaching the posterior chest wall, may be measured by placing the transducer along the left paravertebral posterior chest wall. In circumstances where a dilated ascending thoracic aorta presents to the right of the sternum and reaches the anterior chest wall, its dimensions may be measured by transducer placement in right parasternal positions. Experimental work has shown the feasibility of the ultrasonic detection of dissecting aneurysms of the aorta. Thoracic aortic dissections have been recorded in several patients.