GABAA receptor channels are ubiquitous in the mammalian central nervous system mediating fast inhibitory neurotransmission by becoming permeant to chloride ions in response to GABA. The emphasis of this review is on the rich chemical diversity of ligands that influence GABAA receptor function. Such diversity provides many avenues for the design and development of new chemical entities acting on GABAA receptors. There is also a significant diversity of GABAA receptor subtypes composed of different protein subunits. The discovery of subtype specific agents is a major challenge in the continuing development of GABAA receptor pharmacology. Leads for the discovery of new chemical entities that influence GABAA receptors come from using recombinant GABAA receptors of known subunit composition as has been elegantly demonstrated by the refining of benzodiazepine actions with a1 subunit preferring agents showing sedative properties but not anxiolytic properties. The most recent advances in the therapeutic use of agents acting on GABAA receptors concern the promotion of sound sleep. Many herbal medicines are used to promote sleep and many of their active ingredients include flavonoids and terpenoids known to modulate GABAA receptor function.