Clinically applied techniques for lung preservation of flush perfusion with cold modified blood and core cooling by means of cardiopulmonary bypass were compared in a canine model of single left lung transplantation with immediate ligation of the contralateral bronchus and pulmonary artery. In the cold modified blood group (n = 5) after pretreatment with the synthetic prostacyclin analogue iloprost (20 ng/kg/min), lung preservation was achieved by pulmonary artery perfusion with a solution of autologous donor blood, albumin, and mannitol. In the cardiopulmonary bypass group (n = 7), donors were cooled to an esophageal temperature of 10°C before harvest of the heart-lung bloc. Donor organs were stored at 4°C for 6 hours. After transplantation, artificial ventilation at a fixed oxygen concentration was continued until death or until animals were killed at 24 hours. Assessment of lung preservation was by recipient survival, blood gas analyses, and measurement of total lung water content. All cold modified blood recipients survived for 24 hours; four of seven bypass recipients died within 7 hours of operation. There was no change in oxygenation in the cold modified blood group at 1 hour after contralateral ligation: pao2, 212.2 mm Hg ± 8.5 preligation; 227.2 mm Hg ± 11.5 postligation. Oxygenation in the bypass group was reduced at 1 hour (pao2, 182.6 ± 7.6 mm Hg preligation; 139.8 ± 32.1 mm Hg postligation), but the difference did not reach statistical significance. The difference between groups at 1 hour was significant (p<0.05). Lungs removed from the cold modified blood recipients contained less water than those from cardiopulmonary bypass recipients: 5.22 ± 0.63 ml/kg and 8.64 ± 1.44 ml/kg, respectively, p = 0.06. These data suggest that flush perfusion with cold modified blood achieves successful lung preservation after 6 hours' storage. Core cooling by means of cardiopulmonary bypass yielded inconsistent results in this animal model.