Ten dogs underwent orthotopic cardiac transplantation after preservation of the donor heart for 24 hours in an oxygenated hypothermic, hypertonic, intracellular solution, either with (five dogs) or without (five dogs) continuous, oxygenated, low-pressure perfusion. Eight dogs survived for 24 hours after transplantation, at which time they were put to death. The two nonsurvivors were among the five with nonperfused hearts. Examination of all 10 donor hearts showed differences between the two groups: Four of five nonperfused hearts showed severe transmural myocardial coagulation necrosis but only small foci of contraction band necrosis (myofibrillar degeneration). The perfused hearts, however, showed more extensive subendocardial areas of contraction-band necrosis, but only minimal and focal coagulation necrosis, indicating less severe hypoxic damage. These results indicate that oxygenated perfusion with a hypothermic, hypertonic, intracellular solution may permit improved transplant survival after extended cardiac preservation.