All 1195 male patients aged between 65 and 74 years on the Family Practitioner Committee register for the four group practices in Stroud, UK were invited for a health screening check. The examinations included abdominal ultrasonography to measure maximum aortic diameter, measurement of blood pressure and recording of smoking habits. An attendance rate of 76 per cent was achieved (906 patients). Seventy-one patients (7.8 per cent) were found to have aortic diameters greater than 2.5 cm and 14 (1.5 per cent) had aortic diameters greater than 4.0 cm. Aneurysms were more common in smokers and in hypertensive patients. However, restriction of screening to patients with these risk factors would have led to a number of aneurysms remaining undiscovered. We recommend therefore that ultrasound screening for abdominal aortic aneurysms should be offered to all men between the ages of 65 and 74 years.