The hepatic microcirculation in fatty and normal liver grafts in ACI rats was investigated using in vivo microscopy. Six groups were studied. They were: normal and fatty control livers (sham operated), 6-hr cold University of Wisconsin solution (UW)-preserved fatty and normal liver grafts (survival conditions, fatty and normal liver grafts), 18-hr cold UW-preserved fatty livers (nonsurvival conditions, fatty liver graft), and 24-hr cold UW-preserved normal livers (nonsurvival conditions, normal liver grafts). Fatty livers in all groups were found to have narrow and irregular sinusoids with blood cell adhesions to endothelial cells. The number of adhesions increased as the preservation time increased. Sinusoidal blood flow area decreased as the preservation time increased and was correlated with survival in both normal and fatty liver grafts. The phagocytic activity of Kupffer cells (corrected for flow) increased as the preservation time increased. The phagocytic Kupffer cell activity of the 18-hr preserved fatty liver group was greater than the activity of any other group. These features may cause liver cell death and contribute to primary graft nonfunction after transplantation of a fatty liver.