Background: It is investigated whether preoperative allopurinol administration protects lung injury induced by cardiopulmonary bypass (CPB). Methods: Sixty patients with coronary artery disease who need elective coronary artery bypass grafting operations by using CPB were taken into this study. They were divided into two groups; control and allopurinol. Allopurinol (300 mg/day) was administered to the latter group during the preoperative period of 5 days. Standard CPB procedures were used in all cases. Blood was sampled for TNF-alpha, IL-6, IL-8, IL-10 before anesthesia (T0), after anesthesia and before skin incision (T1), before CPB (T2), after aortic declamping (T3), at the end of CPB (T4), 6 hours after operation (T5), 12 hours after operation (T6), and 24 hours after operation (T7). Pulmonary function test (PFT) was performed before and following the 6th day of operation. Results: TNF-alpha, IL-6, IL-8 increased in both groups at T3, T4, T5 and T6 compared to control (p<0.05). TNF-alpha, IL-6, and IL-8 levels were lower in group A at T3, T4, T5 and T6 (p<0.05). Creatinin phosphokinase (CK) levels were lower in group A at T6 (p<0.05). CK-MB levels were lower in group A than in group C (p<0.05). Pulmonary function test (PFT) did not yield any differences between the groups. Conclusions: Preoperative allopurinol administration decreases the infl ammation and myocardial injury according to biochemical markers of ischemia reperfusion injury. However, this biochemical success does not rebound to PFT (Tab. 5, Ref. 15). Full Text in PDF www.elis.sk.