A highly sensitive and accurate method for the preconcentration and determination of ultratrace amounts of methylphosphonic acid (MPA) in water samples is proposed. The method is based on the solid phase extraction with an ion exchange anion resin. The high capacity anion-exchange was prepared from the reaction of polyvinylbenzyl chloride and 2,3,4-tris((dimethyl amino)methyl)phenol in dioxane. The ion-exchange capacity was estimated by the potentiometric titrations and calculated as 8.6meq/g-dry. The extraction efficiency and the influence of the type and least amount of eluent for the stripping of MPA from the cartridge, pH, flow rates of sample solution and eluent, resin stability and reproducibility, and the breakthrough volume were evaluated. The limit of detection of the method was 0.5 mu gL-1 for MPA and also an enrichment factor of 100 was obtained.