The presence of jaundice in the neonate, infant or young child presents a broad differential diagnosis. The 'disease' may be benign, as in breast-milk jaundice, or potentially fatal, as in hereditary fructose intolerance. The cause of the jaundice may be a primary hepatic disorder, such as extrahepatic biliary atresia, or secondary to a non-hepatic cause, such as haemolysis or sepsis. There may be significant hepatic injury and dysfunction, as in fulminant viral hepatitis, or simply elevation of plasma bilirubin, as in Gilbert's syndrome. In this chapter we will discuss the familial hyperbilirubinaemia syndromes. This diverse group of disorders is characterized by hepatic dysfunction in the absence of hepatocellular injury. The first section of the chapter will discuss the unconjugated hyperbilirubinaemias: Crigler-Najjar syndrome I, Crigler-Najjar syndrome II and Gilbert's syndrome. The discovery of the gene for bilirubin uridine diphosphate glucuronosyltransferase has increased our understanding of the genetic heterogeneity and clinical presentation of the Crigler-Najjar syndromes. The remainder of the chapter will discuss the conjugated hyper-bilirubinemias: Rotor syndrome and Dubin-Johnson syndrome. These rare diseases share many clinical features; however, they can be readily distinguished by biochemical markers in the urine and bile.