Metabotropic glutamate receptors (mGluRs) are members of the group C family of G-protein-coupled receptors. Eight different mGlu subtypes have been identified and classified into three groups based on amino acid sequence similarity, agonist pharmacology, and the signal transduction pathways to which they couple. They perform a variety of functions in the central and peripheral nervous systems, being involved in learning, memory, anxiety, and the perception of pain. They are found in pre- and postsynaptic neurons in synapses of the hippocampus, cerebellum, and cerebral cortex, as well as other parts of the bain and peripheral tissues. This volume will focus on the latest research in the role of Group I mGluRs in health and disease.