The level of blood lipids and apolipoproteins in subjects being screened for abdominal aortic aneurysms have been investigated. As part of an ultrasound screening programme in a population of 65- to 75-year-olds, blood samples were collected from 1460 of 1504 subjects with a normal aorta (97.1%) and 69 of 70 patients with an abdominal aortic aneurysm >29 mm (99%). Samples were also taken from 22 of 27 patients (81%) with an ectatic aorta (26–29 mm). Total cholesterol, HDL-cholesterol, LDL-cholesterol, Apo-AI and Apo-B levels were significantly higher in women than in men ( P < 0.01). Levels of HDL-cholesterol and Apo-AI were significantly lower in patients with an abdominal aortic aneurysm than in normal subjects ( P < 0.001). The mean (s.d.) body mass index was 25.1 (3.9) in women and 25.5(3.2) in men with aneurysms and not significantly greater than that of normal subjects (25.2(3.61) and 25.2(3.38) respectively). Copyright © 1996 The International Society for Cardiovascular Surgery.