A technique of auxiliary liver homotransplantation in rats was developed by considering both the functional competition and unfavorable hemodynamics to which a heterotopic liver graft is exposed. Atrophy of the graft was prevented by partial hepatectomy, ligation of the common bile duct, and diversion of the portal blood from the remaining host liver. An outflow anastomosis was reestablished as proximally as possible, using a short cuff of the donor vena cava to keep the distance between the graft and the right atrium short and the venous outflow pressure low, thus avoiding congestion of the graft. Only 30% of the donor liver was used as a graft, which was provided with portal inflow only. Under these conditions the grafts hypertrophied, and about 44% of the rats survived longer than 14 months.