Objective: Aortic aneurysm has traditionally been considered a manifestation of atherosclerosis, but recent evidence suggests an independent pathogenesis, possibly similar to that of chronic obstructive pulmonary disease (COPD). Further insight into the pathogenesis of aortic aneurysm might be obtained by comparing its association with smoking with that of other smoking-related diseases. Study design: We conducted a systematic review of studies providing relative risk associated with smoking for both aortic aneurysm and other smoking-related diseases. Results: We identified 10 eligible studies, which included more than 3 million subjects. The events reported in 9 studies were death from target diseases; the tenth study reported new diagnoses. Relative risk for aortic aneurysm-related events in current smokers was generally 3 to 6, compared with 1 to 2 for coronary artery disease or cerebrovascular disease and 5 to 12 for COPD. For each category of smoking in each study, relative risk associated with smoking was substantially greater for aortic aneurysm than for coronary artery disease or cerebrovascular disease. Our pooled estimates indicate that, in men, the association of ever smoking with aortic aneurysm is 2.5 times greater than the association of ever smoking with coronary artery disease (95% confidence interval [CI], 2.2, 2.8) and 3.5 times greater than the association of ever smoking with cerebrovascular disease (95% CI, 2.4, 5.3), but only 0.56 as great as the association of ever smoking with COPD (95% CI, 0.36, 0.86). Conclusions: The difference in magnitude of these associations with smoking is consistent with a non-atherosclerotic cause for aortic aneurysm and/or a stronger effect of smoking on vascular disease in the peripheral arteries.