Eleven rat livers were stored at 7 degrees C for 24 or 48 hr using a continuous nonpulsatile perfusion method. The perfusate was based on the isotonic citrate preservation solution but contained, in addition, gelatin polypeptides (Haemaccel, Hoechst) and fluorocarbon emulsion (FC-43, Green Cross Corp.). Isologous livers were orthotopically transplanted after preservation, and long-term survival was 3/6 following 24 hr preservation and 4/5 following 48 hr preservation. All the biopsies taken immediately after revascularization were histologically normal. The seven surviving animals were killed at two months and histology showed biliary obstruction, but in all cases the hepatocytes appeared to be well preserved. These late histological findings are common in any use of this transplantation model and are believed to be associated with the difficulty of obtaining a satisfactory anastomosis of the bile duct. The perfusate described here is capable of providing reliable 48 hr preservation of the rat liver.