Crigler-Najjar syndrome is an inborn error of metabolism caused by a point mutation in one of the five exons of UGT1A1 gene, the product of which is responsible for elimination of bilirubin via bile. A number of hyperbilirubinemia disorders similar to Crigler-Najjar syndrome are reported, but they differ in their level of unconjugated bilirubin and responses to the treatment. The gene discussed is UGT1A1; the disease is Crigler-Najjar syndrome.