Acute liver failure in children and adults is associated with a high mortality rate. At present the treatment of choice is orthotopic whole-liver transplantation. However, allogeneic liver transplantation necessitates lifelong immunosuppressive therapy, which is associated with substantial risks to the patient. Temporary auxiliary partial orthotopic liver transplantation has been developed recently as an alternative, enabling the native liver to regenerate while avoiding the risks of long-term immunosuppressive treatment. Here we describe two cases of partial orthotopic liver transplantation in children. Auxiliary partial orthotopic liver transplantation was performed in two boys (5 and 6 years old) suffering from acute liver failure of unknown origin. The native left lateral liver lobes (segment II and II) were removed and replaced by left lateral liver grafts from young blood-group-compatible adults. In the first child the native liver, which was 80% necrotic at time of transplantation, showed regeneration within two weeks and the partially necrotic graft could be surgically removed on day 15 after auxiliary transplantation. Four years after transplantation, the child is in excellent condition with normal liver function and does not require any treatment. In the second case the native liver (90% necrotic at time of transplantation) regenerated within 6 weeks of transplantation, at which time the transplanted liver was removed. The patient developed aplastic anemia and died 2 months after transplantation from candida sepsis. The conclusion was that auxiliary partial liver transplantation in childhood provides a valuable option to maintain liver function in acute liver failure until functional recovery of the native liver. The main advantage over whole-liver transplantation is the chance to avoid lifelong immunosuppression. However, there is a higher surgical risk. Therefore, auxiliary transplantation should be considered carefully in every case of acute liver failure in children.