A solvent, 1,4-butanediol, is also abused as a recreational drug. In mammals, 1,4-butanediol is metabolized into gamma-hydroxybutyric acid (GHB), which stimulates metabotropic gamma-aminobutyric acid (GABA) GABAB and putative GHB receptors. Here we show that in vivo injection of 1,4-butanediol into adult Drosophila leads to GHB synthesis (GHB was detectable 5 min after 1,4-butanediol injection and increased dramatically 1-2 h later). This synthesis of GHB was accompanied by an impairment of locomotor activity that was mimicked by a direct injection of GHB into flies. We propose Drosophila as a model to study the molecular actions of 1,4-butanediol and GHB.