Studies have demonstrated that cardiopulmonary bypass (CPB) adversely affects pulmonary circulation, which is involved in metabolism in the lung, and that pulmonary circulation after CPB can restore the prostaglandin E2 (PGE2) level mainly standing for levels of key vasostimulators augmented during CPB, which may influence systemic tissue perfusion and body oxygen metabolism. However, in lung transplantation (Lx), pulmonary circulation is restored to the graft, which might induce another CPB reaction. We prospectively examined the influence of CPB on body oxygen metabolism in Lx. Left Lx was successfully performed on 10 dogs (group-on: with normothermic CPB without cardiac arrest, group-off. without CPB; n = 5 vs. 5). At 30 minutes after graft perfusion, the right pulmonary artery and bronchus were clamped. Body weight, donor-to-recipient body weight ratio, and clinical parameters were comparable between the two groups, except for the hematocrit level during CPB. At 90 minutes after graft perfusion, mixed venous oxygen saturation (SVO2) was lower (p < 0.01) and 02 extraction rate (p < 0.01), PGE2 (p = 0.025), and arterial blood ketone body ratio (KBR) (p < 0.01) were higher in group-on than in group-off, whereas these parameters were comparable before graft perfusion between the two groups. 02 consumption and acetic acid were higher in group-on than in group-off, whereas 0, delivery and 3-hydroxy propioic acid were comparable between the groups. In conclusion, Lx during CPB may induce a new inflammatory reaction and influence body oxygen metabolism, contrary to the restoration of pulmonary circulation after CPB.