Recent molecular studies have resulted in the identification of genetic alterations underlying several hereditary disorders of the liver. Cloning of disease genes are increasing our understanding of the basic defects in liver diseases. This review focuses on selected inherited liver diseases such as hyperbilirubinemic syndromes, hemochromatosis, Wilson disease and genetic cholestatic syndromes and illustrate the knowledge gained on these disorders from molecular studies. Potential implications of the identification of disease genes such as practical applications for diagnosis, information on prognosis and the possibility to design new therapies are discussed.