A new solution which can extend successful preservation times for hepatic allografts was recently developed at the University of Wisconsin (UW). To examine the mechanism of improved viability using this solution, we developed a model of orthotopic hepatic transplantation in the rat. As a baseline study, we compared parameters of viability of allografts preserved in Collins solution to those preserved in UW, including survival, bile output, peak AST, and allograft weight change during storage. Seventy-four rats were transplanted following storage in Collins solution and 70 rats were transplanted after storage in UW. Cold-storage time varied between 2 and 24 hr. The survival with preservation in UW was significantly better than that with Collins when storage time was greater than 2 hr. The preservation time for a viable organ using UW was greater than double that using Collins. The peak AST using UW was lower than that with Collins for cold ischemic times (CIT) up to 10 hr, with significance demonstrated at 5-6 and 7-8 hr when compared with Collins. Prolonged CIT resulted in an increase in liver weight with Collins-preserved livers and a decrease in weight with UW-preserved livers. Using a model of orthotopic liver transplantation in the rat, we demonstrated a doubling of preservation time when UW solution was substituted for Collins. Similar improvements in recipient survival and biochemical parameters of injury have been demonstrated in the canine model and in human clinical trials.