Changes in the sinusoids of rat livers stored in cold (2 degrees C) Euro-Collins solution for various periods were observed using combined scanning (SEM) and transmission electron microscopy (TEM). The sinusoidal endothelial cells were vulnerable to cold ischemia. Fenestrations of the endothelial cells were enlarged and became mesh-like after a 4-h preservation period. Following 8 h storage the sieve plates and cytoplasmic processes of the endothelial cells were destroyed and there was a tendency for the perikaryon to desquamate. Blebs derived from hepatocytes were seen after 4 h and these increased in number and size with prolonged preservation. Although the sinusoids were filled with blebs after 24 h preservation. no irreversible ultrastructural damage in the parenchymal cells was observed. Within 12 h storage, the liver had a mosaic pattern after perfusion fixation indicating uneven fixation and profound circulatory disturbance. These results suggest that endothelial cell destruction and/or numerous blebs may have unfavorable effects on the microcirculation of the transplanted liver after prolonged preservation.