Gamma hydroxybutyrate (GHB) is primarily known and used as a relatively specific inhibitor of central DA release. However, it is also widely assumed to be an agonist or prodrug of gamma-aminobutyric acid (GABA) and its central activity has been attributed to an action exerted at GABA receptors. Nevertheless, there is compelling evidence that: (1) GHB formation may occur independently of GABA; (2) GHB is behaviorally, biochemically and physiologically distinct from GABA in many ways, and does not consistently effect GABAA or GABAB agonist induced responses; (3) GHB has little effect on either GABAA or GABAB receptors at less than millimolar concentrations. Consequently, GHB does not appear to be either a GABA prodrug or a GABA agonist. However, the GHB metabolite gamma butyrolactone (GBL) may possess some limited GABA agonist activity.