The fine structure of the pig liver was examined after 30 min of warm ischemia at 37 degrees C, after 2 h of cold ischemia at 4 degrees C and after 30 min of warm ischemia followed by a further 30 min of cold ischemia. After warm ischemia, limited mitochondrial swelling was observed in hepatocytes. After cold ischemia, alone or following warm ischemia, vesiculation and vacuolation of the hepatocyte cytoplasm and appearance of intrasinusoidal blebs deriving from hepatocytes were observed with different intensity among the animals. These findings suggest that cooling and storing the liver at 4 degrees C may lead to injury, which could negatively influence the viability of the organ, with different intensity from case to case.