This up-to-date introduction to the blood-brain barrier starts with a clear description of the key historical experiments which have led to the concept of this multi-faceted barrier mechanism. There are sections on the morphology of the barrier, basic transport kinetics and carrier-meditated processes. Subsequent chapters deal with transport of glucose and amino-acids, peptides and nucleotides. The final chapter reviews various models of neurological disorders which can be used to unravel the complexity of the barrier in health and disease.