The blood-brain barrier (BBB) is a highly regulated system that maintains brain allostasis. BBB achieves its main function by transporting blood to brain glucose, amino acids and other molecules needed for proper neural physiology, while extruding from the brain molecules derived from neural and glial metabolism that may have neurotoxic properties. In this book, the authors present topical research in the study of blood-brain barriers including their local and temporal regulation during normal and altered physiological states; the therapeutic opportunities of efflux-transporters at the blood-brain barrier; novel strategies to restore blood-brain barrier integrity after brain injury; evaluation of the blood-cerebrospinal fluid barrier in neurological diseases and blood-brain barrier in hepatic encephalopathy.