Increased numbers of polymorphonuclear granulocytes (PMN) in the airways, as measured by PMN content in bronchial lavage fluid (P<0.01), were found 3 h postoperatively in ten patients undergoing surgery for lumbar aortic aneurysms. An increase in plasma levels of the complement split product C3dg from 6 (0–19) AU/ml preoperatively to 20 (13–50) AU/ml 3 h after surgery (P<0.01), indicates an activation of the complement cascade. These changes were not accompanied by increased elastase activity in the bronchial lavage fluid or by major changes in pulmonary blood gas exchange or vascular resistance, indicating that massive PMN activation, analogous lo that proposed in adult respiratory distress syndrome (ARDS) had not taken place. In conclusion, complement system activation and migration of PMN into the airways, as seen in connection with major vascular surgery, does not seem to contribute to ARDS‐type pulmonary dysfun