In this thesis studies on auxiliary partial liver transplantation in the dog and the pig are reported. The motive to perform this study was the fact that patients with acute hepatic failure or end-stage chronic liver disease are often considered to form too great a risk for successful orthotopic liver transplantation. Auxiliary partial liver transplantation may offer a solution for those patients. In the introduction to this thesis in Chapter 1 the indication for liver transplantation is discussed. Potential advantages of auxiliary liver transplantation compared with the orthotopic technique are lined out. The results in the limited number of patients so far treated by auxiliary liver transpl~~tation are reported. A review is given of the literature on experiments in laboratory animals in which the technique of auxiliary liver transplantation was tested. Attention is focussed on problems of space, position and blood supply to the graft. It appeared that optimal conditions in auxiliary liver transplantation demands small or partial donor livers and that the transplant should have a low outflow pressure, adequate hepatic arterial inflow as well as adequate inflow of portal venous blood. Problems related to biliary drainage and rejection are discussed. The essential part of this thesis is our own experimental work, reported in the Chapters 2, 3, 4, 5, and 6. A surgical technique of auxiliary partial liver transplantation was developed and studied in the dog and the pig. In porcine experiments metabolic support of auxiliary partial liver transplants in the presence of acute host liver failure was investigated. All experiments were performed in the Laboratory for Experimental Surgery of the Erasmus University, Rotterdam. The five chapters are written in the form of scientific papers. Chapter 2, 3. 4 and 5 have been published (2, 5) or have been accepted (3, 4) for publication. Chapter 6 has been submitted for publication