This article is the ninth in a series on the biological basis of child health and follows on from the previous article, which discussed the gastrointestinal system. The liver is the largest solid organ in the body and has more than 500 functions. These functions include: producing bile, which serves as a vehicle for waste products and as an aid for the digestion of dietary fat; synthesising most coagulation factors, needed in the clotting cascade; and transforming glycogen into glucose for use as energy in cell metabolism. While most liver conditions seen in children are rare, it is important that children’s nurses can identify the clinical features of childhood liver disease. This article provides an overview of the embryological development of the liver, its anatomy and functions, liver function tests in children, and the clinical features and pathophysiology of childhood liver disease.