The cerebrospinal fluid (CSF) is a clear colorless fluid found in the brain and the spinal cord. It acts as a cushion for the brain, providing basic immunological and mechanical protection to the brain inside the skull. It serves an important role in cerebral autoregulation of cerebral blood flow. The brain produces approximately 500 ml of cerebrospinal fluid everyday. The blood brain barrier (BBB) is a selective semipermeable boundary separating the circulating blood from the brain and the extracellular fluid of the central nervous system. It restricts the diffusion of solutes in the blood and hydrophilic molecules into the CSF but allows the diffusion of hormones, oxygen, carbon dioxide and other polar molecules. The blood brain barrier acts to protect the brain from circulating pathogens. In cases where an infection occurs, a drug has to be administered directly into the CSF such that it can cross over into the blood-cerebrospinal fluid barrier. This book contains some path-breaking studies in the physiology of the cerebrospinal fluid and blood brain barriers. It will also provide interesting topics for research, which interested readers can take up. Coherent flow of topics, student-friendly language and extensive use of examples make this book an invaluable source of knowledge.