We have previously reported that aortic tissue elastase increases with operative trauma unrelated to direct aortic injury in rabbits and that increased tissue elastase may be responsible for abdominal aortic aneurysm (AAA) rupture in humans. In the current study we studied the levels of human neutrophil and serum proteolytic activity in response to elective surgical trauma. Serum elastase, neutrophil elastase and alpha-1-antitrypsin (A-1-AT) were determined in 20 patients undergoing elective coronary artery bypass grafting. Neutrophil proteolytic activity was significantly lower the day of surgery and on postoperative day 6 while serum proteolytic activity was significantly higher the day of surgery and on postoperative day 6 compared to preoperative values. If increased serum proteolytic activity increases the chance of rupture of an AAA, then the release of neutrophil elastase may provide a mechanism whereby asymptomatic AAAs rupture after unrelated elective surgery.