Glutamate receptors (GluRs) in the central nervous system have been the subject of intense investigations for several decades, providing new avenues for the understanding of excitatory neurotransmission, excitotoxicity, mechanisms of injury, and therapeutics for several acute neurological conditions, such as brain trauma, and for neurodegenerative and neuropsychiatric disorders including addictions, Alzheimer disease, etc. Evidences of GluRs beyond the central nervous system were first reported in the early 1990s. When the idea of this book was conceived, the knowledge, specificity, and functional significance of GluRs in peripheral tissues was still in its embryonic stage. From our perspective, the idea of GluRs in peripheral tissues arose from our research on seafood toxins (see Chapter 1), and has now been reinforced by the results of other scientists working in similar areas. In this book, we have invited some of the leading authorities in the field to summarize their findings and to provide a framework for further investigations. The book is divided into three sections— Part I is on general concepts and concentrates on the distribution and cell-specific localiza tion of glutamate receptors, their transporters, and the pharmacology in peripheral tissues and organs. Part II emphasizes the presence and implications of these receptors in specific target tissues, organs, and systems, including liver, lungs, endocrine tissues, bone, immune system, etc. Part III focuses on glutamate receptors in plants to illustrate their presence beyond the animal kingdom.