HTK (histidine-tryptophane-ketoglutarate) organ preservation solution has been shown to be effective in human kidney transplantation, but the efficacy of HTK for extended liver preservation has not been determined. In this study, canine livers were preserved in HTK and compared with livers preserved in University of Wisconsin solution. First, the right and left liver lobes in dogs were flushed separately with cold HTK and UW, respectively, according to a double-flush method. After splitting the liver, the right and left lobes were stored at 4$dGC in either solution for 24 hr and 48 hr and assessed microscopically for parenchymal cell swelling, and enzyme histochemically for 5′-nucleotidase (5′-NT) as a marker of ischemic liver injury. Unlike livers preserved in UW (n=5), HTK-preserved livers (n=5) showed progressive parenchymal cell swelling after 24-hr and 48-hr storage. The 5-NT scores in HTK livers were lower than in UW livers, indicating increased storage injury (0–5% and 66–85% in HTK- and UW-preserved livers, respectively, after 48-hr storage). Second, graft function was tested in an orthotopic liver transplantation model in the dog. Whole livers were flushed in situ with cold HTK or UW and stored at 4$dGC for 24 hr or 48 hr. Liver grafts stored in HTK were not washed out prior to reflow in the recipient, in contrast to grafts stored in UW. Livers preserved for 24 hr using HTK showed life-supporting function after transplantation (n=5, survival 12 hr-8 days). All grafts preserved for 48 hr in HTK did not function (n=5, survival <10 hr). UW-preserved grafts all functioned after 24-hr storage (n=5, survival >6 days), as well as after 48-hr storage (n=6, survival >6 days). Peak serum glutamic oxaloacetic transaminase (SGOT) values after transplantation of 24-hr and 48-hr HTK-preserved livers did not differ from peak SGOT values of UW-preserved livers after similar preservation times. In conclusion, UW solution is more effective than HTK solution in extended preservation of canine liver grafts: 24-hr storage of livers preserved with HTK solution is feasible, whereas 48-hr storage results in a nonfunctioning graft.