When first encountering an infant or child with cholestatic liver disease, it is essential that diagnostic evaluation be conducted promptly in order to (1) recognize disorders amenable either to specific medical therapy (e.g. galactosemia, tyrosinemia, hypothyroidism, urinary tract infection) or to early surgical intervention (e.g. biliary atresia, choledochal cyst); (2) institute treatment directed toward enhancing bile flow; and (3) prevent and treat the varied medical, nutritional, and emotional consequences of chronic liver disease. Because many of the treatable causes require early diagnosis and prompt institution of therapy, the evaluation of the cholestatic infant should never be delayed. Although “physiologic cholestasis” (hypercholemia or elevated bile acids) may be present in the infant, there is no state of “physiologic conjugated hyperbilirubinemia”. For the jaundiced infant, historical and clinical information such as color of the stools, birth weight, and presence of hepatomegaly may provide important clues as to the etiology of cholestasis. Consanguinity or liver disease in siblings suggests the possibility of metabolic, familial, or genetic disease. Review of the prenatal and postnatal course may reveal intrauterine infection, occurrence of hypoglycemia or seizures, and exposure to toxins/drugs (i.e. total parenteral nutrition (TPN)). Careful physical examination may reveal features of typical disorders or syndromes. For the older child and adolescent, a history of exposure to drugs/toxins (e.g. acetaminophen), the presence of vascular insufficiency, and the presence of underlying disease (e.g. inflammatory bowel disease) provide helpful clues. The diagnostic evaluation of the infant with cholestasis is detailed in Chapter 8.