Kainic acid is a naturally occurring amino acid that is isolated from red algae and is known to cause amnesic shellfish poisoning via the activation of AMPA and kainate receptors in the hippocampus. Kainic acid is an analogue of glutamate and can modulate the transmission of glutamate. It's neurotoxic potency has been shown to be 30 fold that of glutamate. Glutamate is an excitatory neurotransmitter that exerts its postsynaptic effects through ionotropic and metabotropic receptors. Of the ionotropic glutamate receptors (GluRs), kainic acid has a high affinity for 5 subtypes (KA1 and KA2, GluR5, GluR6, GluR7). Kainate receptors play a significant role in the physiological functioning and activity of numerous systems in the brain. This book discusses the neurotoxic properties of kainic acid, as well as the biological sources and clinical applications.