Cardiopulmonary bypass is a common clinical procedure which can be associated with post-operative lung dysfunction. Increased pulmonary vascular permeability accompanied by pulmonary neutrophil sequestration may occur during cardiopulmonary bypass. Because pentoxifylline (PTX) can alter neutrophil-endothelial interactions and decrease neutrophil oxygen radical production, we investigated its effects on circulating leukocytes and platelets during bypass. Ten patients undergoing elective coronary artery bypass grafts with cardiopulmonary bypass were randomly assigned to receive either PTX or placebo.kg−1.After the induction of anesthesia, PTX or placebo was administered in a blind manner. After a loading dose (50 mg) injected in 10 minutes, PTX was infused at a rate of 1 mg.kg−1.h−1. The infusion was discontinued just after the cardiopulmonary bypass was stopped. Blood samples were withdrawn from the arterial line and Swan Ganz catheter before and after cardiopulmonary bypass. During cardiopulmonary bypass, blood samples were obtained from the venous drainage line and ventricular sump. Times of sampling were the following : 1) before induction of anesthesia ; 2) during cardiopulmonary bypass and prior to aortic cross-clamping ; 3) during CPB and just after the release of aortic cross-clamping ; 4) after the discontinuation of cardiopulmonary bypass. To evaluate the effects of PTX on transpulmonary sequestration of circulating leukocytes and platelets, the count of these blood cells was performed on pre and post-pulmonary samples and were corrected according to the blood hemoglobin level. Neutrophil and monocyte adherence was assessed before anesthesia, during and after cardiopulmonary bypass as well as leukocyte chemiluminescence after stimulation with FMLP, PIA and opsonized zymosan.Cardiopulmonary bypass produced neutrophil and monocyte sequestration in the lung (about 40 %). No difference between PTX group and placebo group was observed. A significant decrease of adherence of circulating neutrophils was detected during cardiopulmonary bypass, but no difference between the two groups was found. In both groups, cardiopulmonary bypass did not produce any pulmonary sequestration of platelets as well as any change in neutrophil oxidative burst induced by FMLP, PMA and opsonized zymosan. To conclude the data suggest that PTX at 1 mg.kg−1.h−1 does not prevent neutrophil and monocyte sequestration in the lung during cardiopulmonary bypass. No PTX-induced change in neutrophil function could be detected.