Hyperbilirubinemia in Crigler-Najjar disease type I (CN) can be partially controlled by daily phototherapy, but these children remain at permanent risk of developing brain damage due to kernicterus. Because liver transplantation is the only available curative treatment for liver-based inborn errors of metabolism, orthotopic liver transplantation (OLT) was performed in six patients with CN. Mean age at surgery was 52.5 months (range 27 to 100). Despite a mean daily phototherapy of 12.4 +/- 0.8 hr, mean bilirubin of the 6 patients was 388 microM/L (range 175 to 703) before OLT; one of them was also being treated with tin-protoporphyrin. All 6 had elevated AST/ALT, ranging from 1.4 to 6 times upper normal values. Complications occurred in three patients after OLT, including miliary tuberculosis in one, graft rejection and retransplantation in one, and hepatic artery thrombosis in one. All patients survive with normal serum bilirubin level (follow up 6 to 116 months). Four have normal enzymes on post-OLT follow-up (30 to 95 months), follow a normal education program, and have a normal social life. One recently transplanted patient has progressively normalizing liver function tests 6 months after OLT. One patient transplanted at 8 y.o. (now 116 months post-OLT) has moderate neurological delay due to pretransplant kernicterus, and posttransplant chronic persistent hepatitis. Our series shows that OLT cures hyperbilirubinemia in CN patients, with an excellent survival prospect. The procedure should be decided upon before neurological sequelae occur, since these persist after transplantation.