The physiology of the liver involves metabolism, excretion, and body defense. Within the context of metabolism, the liver is the site of a multitude of biochemical reactions essential to the human organism; included are synthesis, degradation, interconversion, storage, and biotransformation. A working knowledge of the relationship between structure and function and of hepatic processes under normal conditions is essential for understanding the derangements observed in clinical diseases affecting the liver. Our overview of hepatic physiology highlights some of these facets of normal hepatic anatomy and function of special relevance to the physician confronting liver dysfunction and its varied clinical consequences.