Packed capillary column liquid chromatography (LC)-electrospray mass spectrometry (ESI-MS) was used for the first time to detect and identify O-ethyl, S-[2-(diisopropylamino)ethyl] methylphosphonothiolate (VX) and its degradation products, including compounds containing a P-CH3 bond, bis(diisopropylamino)thioalkanes and ureas commonly employed as VX stabilizers. The reported ESI-MS data were generally acquired with a higher sampling cone voltage, a setting that promoted collisionally activated dissociation, and resulted in the acquisition in informative mass spectra containing both molecular and product ion information. The developed method appears to be an attractive alternative to GC-MS for the analysis of aqueous sample containing the degradation products of VX, since they may be analysed directly with little risk of thermal decomposition and without the need for additional sample handling or derivatization. Application of this method to a degraded VX sample resulted in the detection of a number of novel polar and higher-molecular-mass degradation products, not previously associated with VX during GC-MS analysis.