This book provides a comprehensive description of sterols and their novel biological roles in mammalian signaling, the book covers their biosynthesis and structure, describes sterol receptor -mediated actions, their tissue distribution and their role in disease. It offers insight into new research findings, focusing specifically on novel discoveries in bile acid and oxysterol signaling, including the lanosterol-to-cholesterol intermediates. Special attention is paid on the sex distribution of these sterols (male or female) and their sexually dimorphic roles in mammalian species, such as human, rat and mouse. Since sterols and drugs (xenobiotics) use many identical receptor-mediated signaling pathways, the book will be interesting for researchers working on the cross-road of endogenous and xenobiotic metabolism, it is intended for advanced students and scientists in molecular biology and biochemistry as well as for medical doctors in hepatology.