Cardiopulmonary bypass activates the kallikrein-kinin system (KKS). Several groups, including ours, have reported that bradykinin concentrations increase during CPB. For example, Campbell et al demonstrated that bradykinin levels increase 10 to 20-fold during the first 10 minutes of CPB, returned to basal levels by 70 minutes of CPB and remained 1.7 to 5.2-fold elevated after CPB. Plasma and tissue kallikrein were reduced by 80 and 60% respectively, during the first minute of CPB. Similarly, we have demonstrated that bradykinin increases significantly during CPB and that ACE inhibition and smoking potentiate the kinin response during CPB.