Recent studies have investigated the geochemistry of tungsten at the laboratory scale, as well as at field sites, to determine its mobility and toxicity. Tungsten exists in most environmental matrices as the soluble and mobile tungstate anion, although polymerization to form poly- and heteropoly-tungstates can occur. The current study used size-exclusion chromatography (SEC) interfaced to inductively coupled plasma mass spectrometry (ICP–MS) to separate and quantify monomeric and polymeric tungsten species. Direct-infusion electrospray ionization mass spectrometry (ESI–MS) is then used to identify the polymeric species. The SEC method provides quantitative determination of these species in about 10 minutes, and has been applied to deionized water extracts of soils amended with tungsten powder and tissue from plants grown in the tungsten-amended soil. Both soil and plant matrices show monomeric and polymeric tungsten species, including phosphotungstate compounds.