Some diseases that result from inborn errors of critical metabolic or synthetic processes mainly involving the liver do not cause structural liver damage. These disorders can be treated by the addition of liver tissue (auxiliary liver transplantation) rather than liver replacement. We report correction of the metabolic error in a 13-year-old girl with Crigler-Najjar syndrome type 1 by auxiliary (left lateral segment) transplantation. The first graft failed and was replaced successfully. The second graft shows features of chronic rejection, but at 2 years postoperatively bilirubin conjugating ability has not been impaired. Another graft may become necessary in due course.