Pregnancy is the main determinant of some liver diseases in humans: acute fatty liver of pregnancy, cholestasis of pregnancy, and acute liver failure in toxaemia of pregnancy. Pregnancy also modifies the natural history of other more common hepatobiliary diseases, such as cholesterol gallstones. Sex hormones (mainly oestrogens, progesterone and/or some of its metabolites) and prolactin are considered responsible for these pathological consequences and they also appear to be influential in the outcome of several other hepatobiliary disorders, in both sexes and all ages. Although these disorders and their hormonal interrelations have been clinically well characterized, their pathogenesis remains obscure from the biomolecular point of view. In recent years, novel approaches using new technologies have improved our understanding of hormone actions and metabolism, hormone receptors, metabolic pathways and their interrelations with closely related molecules, such as bile acids. This book, the proceedings of the 89th Falk Symposium, held in Santiago, Chile, 10-11 November, 1995, will help research scientists and clinicians to review basic and clinical aspects of these interactions, in order to stimulate biomedical research in a relevant and exciting area.