Pentoxifylline (Ptx) basically decreases necessity of tissue energy via inhibiting 5' Nucleotidase. it alsa decreases celi damage by it's another effect as inhibition of polimorpho nuclear leukocyte (PNL) activation and stabilization of endothelium. The patients to whom open heart surgery was performed divided into two groups. We added Ptx (500 mg/lt) in the prime solution in the study group (n=15) and the usually used prime solution was used in control group (n=10). Malondialdehyde (MDA) and superoxide dismutase (SOD) were studied in the blood that was sampled from the left atrium before cardiopulmonary bypass (CPB) in the both groups. We also examined bronchoalveolar lavage (BAL) that was sampled after CPB in the both groups. Wilcoxon test was used to statistical evaluation. in the study group, we fınd that MDA levels of study group was lower than control group and SOD levels of study group higher than control group. it was statistically signifıcant (p<0.05). At microscopic examination, amount of PNL which was in the BAL of control group were much more higher than study group. We think that Ptx may avoid ischemiareperfusion and reexpansion injury on the lung during CPB.