Trehalose is a nonreducing disaccharide that stabilizes the cell membrane under various stressful conditions. A previous study demonstrated that trehalose was effective in 12-hour canine lung preservation. We have developed new preservation solutions containing trehalose: an extracellular type ET-Kyoto solution (Na 100 mmol/L, K 44 mmol/L) and an intracellular type IT-Kyoto solution (Na 20 mmol/L, K 130 mmol/L). The composition of these solutions is identical except for the electrolyte content. We examined their efficacy in 20-hour lung preservation. Canine lungs were flushed with ET-Kyoto (group A, n = 6), with IT-Kyoto and prostaglandin E1 (25 micrograms/kg) (group B, n = 6), or with Euro-Collins solution and prostaglandin E1 (25 micrograms/kg) (group C, n = 7), and stored for 20 hours at 4 degrees C. Left lung transplantation was performed and evaluated for up to 130 minutes. The flush time was similar in the three groups. Arterial oxygen tensions (inspired oxygen fraction = 0.5) in group A were uniformly excellent (303.3 +/- 7.0 mm Hg 70 minutes after reperfusion and 303.0 +/- 19.6 mm Hg 130 minutes after reperfusion) and significantly higher than in group B (202.6 +/- 32.0 mm Hg, p < 0.05, and 197.8 +/- 44.0 mm Hg, p = 0.054, respectively) or group C (185.9 +/- 23.0 mm Hg, p < 0.01, and 155.7 +/- 36.3 mm Hg, p < 0.05, respectively). Peak inspiratory pressure in group A was significantly lower than in groups B and C (p < 0.05). Wet/dry weight ratio in group A was significantly lower than in groups B (p < 0.05) and C (p < 0.01). Histologic and scanning electron microscopic examinations showed better preservation in group A than in groups B and C. We conclude that ET-Kyoto is superior to IT-Kyoto and to Euro-Collins solution for 20-hour lung preservation.