A series of 227 patients with suspected abdominal aortic aneurysm was studied by continuous ultrasonic "B" scanning. The precise diagnosis has been confirmed by surgery, autopsy, or angiography in 91 patients. The predicted ultrasound diagnosis was correct in all but 1 of the 91 cases. Additional aortic pathology was accurately demonstrated including intraluminal thrombus, dissections, false aneurysm, teflon grafts and aneurysmal involvement of the iliac arteries. In 136 patients, including 29 diagnosed as abdominal aneurysm, no confirmation is yet available.