Heterotopic auxiliary liver transplantation in rats was performed with a portal afferent blood supply, together with either the infra- or suprahepatic part of the inferior vena cava (IVC) as the efferent vessel. Animals in which the suprahepatic part of the IVC was used had a high postoperative mortality which was associated with moderate or severe congestion of the graft in over one-half of the cases. Substitution of the infrahepatic part of the IVC prevented the congestion and increased the postoperative survival rate.