GABA is the major inhibitory neurotransmitter in the CNS, binding to fast-acting ionotropic GABAA receptors to cause inward flux of Cl-resulting in membrane hyperpolarization and thus reducing membrane excitability. Excessive stimulation of these receptors can lead to sedation and ataxia whereas attenuation leads to arousal, insomnia and anxiety. Since modulation of these receptors has such profound physiological effects they have become important drug targets for the treatment of many conditions e.g. anxiety, epilepsy, sleep disorders and for anesthesia. GABAA receptors are pentameric structures typically consisting of alpha, beta and gamma2 subunits in a stoichiometry of 2:2:1. The specific subunit composition is especially important since various combinations mediate different effects. For example, alpha1-containing receptors, accounting for 60% of all GABAA receptors, mediate the sedative/hypnotic effects of benzodiazepines (BZPs) whereas the anxiolytic effects of these drugs are mediated by receptors containing alpha2 and alpha3 subunits. Hence, developing selective allosteric modulators for these latter subunits should ultimately lead to anxiolytic drugs devoid of unwanted sedative effects.