Most polymer membranes with a high ion-exchange capacity (IEC) are not dimensionally stable in water because of their excess water uptake, In this study, an anion-exchange membrane was synthesized by performing a porefilling polymerization in a porous polyethylene membrane used as the supporting substrate. The membrane was found to exhibit a high IEC (3.0 meq/g) but a very low water uptake (8%) and low electrical resistance (0.30 Omega.cm(2)). The membrane capacitive deionization (MCDI) cell assembled from components including the fabricated anion-exchange membrane and a commercial cation-exchange membrane (CMX) was found to exhibit a higher salt adsorption capacity and a higher current efficiency than that using a commercial anion-exchange membrane (AMX, IEC = 1.5 meq/g, electrical resistance = 4.8 Omega.cm(2)) and CMX. This improved performance compared to that of the AMX cell is ascribed to the higher IEC of the new membrane and its lower electrical resistance.