BACKGROUND: Lung transplantation (LTx) is an effective treatment for end stage lung disease. However, the shortage of donor lungs has been a major limiting factor to increase the number of LTx. Ex vivo lung perfusion (EVLP) is a currently approved method to evaluate lung function and to repair donor lung with poor function. The purpose of this study was to develop EVLP system in pig model and to maintain lung function during 4 hours of EVLP. METHODS: Bilateral lung blocks were harvested from five 40 kg pigs. These blocks were applied in EVLP perfused with 37degrees C Steen solution. We performed arterial blood gas (ABG) analyses before death and also every 1 hour for 4 hours after application of EVLP and calculated oxygen capacities (OC) using the results of ABG. We also calculated pulmonary vascular resistance (PVR) and peak airway pressure (PAP) every 1 hour for 4 hours. After EVLP procedure, we excised specimens for pathologic review. RESULTS: We found that OC gradually decreased during the 4 hour period of EVLP; however, no statistically significant difference was obtained. PVR declined sharply after 1 hour of EVLP (P=0.031) and then remained constant for 3 hours. PAP significantly increased after 3 hours (P<0.0001). Pathologic investigations revealed various findings from normal lung to severe pulmonary edema. CONCLUSIONS: On the results of this study, we could preserve the lung function for 4 hours using EVLP. We conclude that application of EVLP in clinical setting can make more donor lungs available for LTx. However, we also understand that more studies and training are needed in clinical practice.