Prospective studies evaluating risk factors for abdominal aortic aneurysm are few. We studied the association of life-style factors with risk for abdominal aortic aneurysm among 29,133 male smokers 50-69 years of age, participants in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study. During a mean follow-up of 5.8 years, 181 were diagnosed with ruptured abdominal aortic aneurysm or nonruptured abdominal aortic aneurysm plus aneurysmectomy. Risk for abdominal aortic aneurysm was positively associated with age [relative risk (RR) = 4.56, 95% confidence interval (CI) = 2.42-8.61 for > 65 vs 40 vs 160 vs 100 vs 6.5 vs 1.5 vs