Since the discovery some 15 years ago of benzodiazepinemodulatory sites associated with GABA A receptors, greateffort has gone into understanding their molecularpharmacology and into developing new anxiolytic drugs thatinteract selectively with them. Prominent in this researchhas beenthe discovery that ~-carbolines, a differentchemical class from benzodiazepines, also act at thesereceptors but that their effects are sometimes quitedifferent from those of the benzodiazepines.This bookdocuments the latest discoveries in the molecularbiology of the GABA A receptor and reveals howan integration of the results of research inmolecularbiology, synthetic chemistry, biochemical and behavioralpharmacology, and clinical pharmacology has paved the wayforthe development of ~-carbolines from substances inducinganxiety and convulsions to a novel therapy for anxietystates, achieving a behavioral selectivity through selectiveactions at subtypes of receptors.