In the rat model of heterotopic auxiliary liver transplantation, the coexistence of the engrafted liver and the recipient's native liver makes it difficult to evaluate the posttransplant graft viability. In this study, auxiliary liver transplantation was performed in Wistar rats, in which the recipient's native liver was handicapped with a 68% partial hepatectomy and a common bile duct ligation. Serum biochemistry of the liver was analyzed and compared with that of the selected control group. The surgical handicap of the liver showed severe damaging effects: the handicapped native livers appeared atrophic at autopsy, and no long-term animal survival could be achieved without an auxiliary liver transplantation. As the engrafted liver corrected the cholestasis of the handicapped native liver, significant differences of serum biochemistry were found between the transplanted group and the control group: for bilirubin concentration and gamma glutamyl transferase activity from postoperative day 3 to 28 (p<.05); for alkaline phosphatase on days 3, 7, 14, and 28 (p<.05); for alanine aminotransferase activity on days 3 and 14 (p<.05); and for aspartate aminotransferase activity on day 14 (p<.05). The efficiency to induce hepatic failure and to hamper its regeneration capacity in the native liver makes animal survival and liver biology as reliable parameters to evaluate the posttransplant graft viability in this rat model.