Astrocytes (literally 'star-formed cells') have the most complex role of all glia cells. Although overlooked during many decades, astrocytes have gained unexpected attention in recent years. Their contribution to glutamate homeostasis is indeed paramount. Altered glial-neuronal interactions play crucial roles in many neurological and neuropsychiatric disorders. This book presents an overview over brain metabolism in epilepsy, hydrocephalus and schizophrenia in general, and glutamatergic metabolism and astrocytic function in particular.