Biochemical, pharmacological and electrophysiological techniques have been used to characterize GABAA receptor (GABAR) channels in mammalian brain and have demonstrated the existence of a population of similar, yet distinct, receptor isoforms. Application of molecular biological techniques has revealed a multiplicity of GABAR subunits and subunit subtypes that must assemble to form the different functional GABAR isoforms. Additionally, the sequencing of numerous genes for GABAR subunits has revealed numerous structural motifs which are potentially important for receptor regulation. This review summarizes recent experimental results with recombinant GABARs which provide insight into how the GABAR subunit subtypes confer different pharmacological properties (most notably benzodiazepine modulation) on different GABAR isoforms, how GABAR subunits assemble to form functional ion channels similar to native GABAR channels and how phosphorylation of GABAR channels regulates their function.