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.