University of Wisconsin solution has been used successfully in clinical kidney and liver preservation. The object of this study was to determine if low-potassium UW (LPUW) solution could be applied to pulmonary preservation. Rabbit lungs were stored after hypothermic pulmonary artery (PA) flush with four different solutions (group 1: Low-potassium dextran (LPD) solution, group 2: High-potassium UW (HPUW) solution, group 3: LPUW solution, group 4: Modified Euro-Collins (E-C) solution). The lungs were preserved at 10°C for 30 hr and evaluated in an ex vivo ventilation/perfusion apparatus using fresh pooled venous rabbit blood. Mean PA flush pressures (MFP) during harvesting were significantly lower in groups 1 and 3 (8.1±1.0 mmHg and 7.3±0.6 mmHg, respectively; mean ± SEM) than in groups 2 and 4 (15.5±1.7 mmHg and 12.3+0.9 mmHg, respectively). Lungs in groups 1 and 3 showed significantly higher PaO2 (103.5±8.0 mmHg and 89.3±7.2 mmHg) than groups 2 and 4 (48.3+7.7 mmHg, 66.7±4.7 mmHg). Groups 1 and 3 showed significantly lower wet/dry weight (W/D) ratios after reperfusion (6.21±0.15 and 6.39±0.23) than groups 2 and 4 (7.70+0.57 and 7.13±0.21, respectively). There were no significant differences in MFP, PaO2, PaCO2, mean pulmonary artery pressure, or W/D ratio between groups 1 and 3. These results suggest that LPUW solution may be as beneficial as LPD solution for pulmonary arterial flush and lung preservation.