Although the inhibitory role of gamma-aminobutyric acid (GABA) in the visual system has been recognised for some time, important new insights into the function of GABA have been made in the last few years. As a result of advances in the field of neurotransmission, there are now accurate morphological and synaptic descriptions of GABA neurons. Computer morphometry techniques allow three-dimensional reconstruction of GABAergic networks to measure distributions and morphologies of GABA neurons and receptors. Availability of specific ligands and antibodies to GABA receptor subtypes, have advanced understanding of selective distribution of these subtypes and their roles in gating actions of GABA. Patch clamp techniques in cell culture have made it possible to study the channel properties of GABA cells. This volume brings together a summary of current understanding of the organization and function of GABA in the visual system. It provides a comprehensive overview of the GABA function, reveals the vital inhibitory mechanisms common amongst all the visual structures, and illustrates the similarities and differences in GABA organization in the different regions of the visual brain.