A poly(vinyl alcohol) membrane (PVA) was modified by radiation graft copolymerization of acrylic acid/styrene (AAc/Sty) comonomers. The Cu and Fe iontransport properties of these membranes were investigated using a diaphragm dialysis cell. In the feed solution containing CuCl 2 or a mixture of CuCl 2 and FeCl 3 , the PVA-g-P(AAc/Sty) membranes showed high degrees of permselectivity toward Cu 2Ο© rather than toward Fe 3Ο© . The permeation of Cu 2Ο© ions through the membranes was found to increase with decrease in the grafting yield. However, as the content of Cu 2Ο© ions in the Cu/Fe binary mixture feed solutions decreased, the rate and the amount of transported Cu 2Ο© through the grafted membrane decreased, with no appreciable permselectivity toward Fe 3Ο© . When Fe 2Ο© ions were used instead of Fe 3Ο© ions in the feed solution containing Cu 2Ο© , the transport of both Cu 2Ο© and Fe 2Ο© through the membrane was observed. The rate of transport of Fe 2Ο© was higher than that of Cu 2Ο© . In addition, it was found that the selective transport of ions was significantly influenced by the pH difference between both sides of the membranes. As the pH of the feed or the received solution decreased, both Cu 2Ο© and Fe 3Ο© passed through the membrane and were transported to the received solution. The role of carboxylic acid and the hydroxyl groups of the grafted membranes in the transportation process of ions is discussed.