Satisfactory extended preservation of the lung has been difficult to obtain. This study investigated the influence of different total volumes and flow rates during flush-perfusion of the lung, and their effect on pulmonary artery pressure, flow distribution, regional lung temperature and functional performance of the lungs following transplantation after 24 hours. Fifteen mongrel dogs served as donors of the heart and lung block. Cold modified Euro-Collins solution was used as flush perfusate. Pulmonary artery and perfusion-line pressures were measured. The regional lung temperature was measured at one minute intervals with 5 myocardial temperature probes. Flow distribution was determined with micro-aggregated albumin labelled with Technetiurn 99. The heart-lung block was harvested, the right lung removed, and samples taken for gammacounting. The left lung was stored in cold Euro-Collins solution and then transplanted. The inspired oxygen fraction (FiO2) was set at 0.4 and was kept constant throughout the procedure and the entire postoperative course. There were 3 groups of 5 animals each. In group A, the flush perfusate was administered at a total volume of 20 cc/kg over a period of 6 minutes. In group B the same volume of perfusate was administered at a pulmonary artery pressure (PAP) of 18 to 20mmHg, resulting in a considerably shorter perfusion time (1.3 minutes). In group C 60 cc/kg of perfusate were given at the same flow rate as in group B, also resulting in PAP of 18 to 20mmHg, but the perfusion time was increased to 4 minutes. Thus, groups B and C investigated the effect of increased pressure and volume of perfusate, respectively. Flush perfusion at higher flow rates (groups B and C} resulted in lower temperatures and a more uniform distribution of the Euro-Collins solution. Postoperatively, survival was improved in groups B and C as compared to group A. Moreover, superior oxygenation and less increase in lung water was seen in group C. Flush perfusion at high volumes and flow rates therefore, appears to be necessary for optimal results in lung preservation.