In keeping with the inflammatory paradigm of abdominal aortic aneurysm (AAA) pathophysiology, in vitro studies suggest that aneurysms secrete the proinflammatory cytokine interleukin‐6 (IL‐6). Circulating IL‐6 levels are higher in patients with AAA with elevated circulating IL‐6 an independent risk factor for cardiovascular mortality. To investigate whether aneurysms secrete IL‐6 into the circulation, arterial IL‐6 was measured from within the aorta in three groups of patients undergoing endovascular procedures; 27 AAA, 10 thoracic aneurysms (TA), and 15 controls. Overall, IL‐6 was higher in the aneurysm groups (P < 0.0008) with significant rises corresponding to positions downstream to the aneurysm in both AAA and TA. There were no significant differences in IL‐6 with aortic position in the control group. These data support the hypothesis that aneurysms secrete IL‐6 into the circulation and may account for the high cardiovascular mortality observed in patients with aneurysms.