An ultra-thin anionic exchange layer was deposited on the surface of a Nafion(R) membrane. This layer was deposited from ethylene and ammonia using a glow-discharge plasma polymerization technique. The scanning electron microscopy (SEM), Fourier transform infrared attenuated total reflection (FTIR-ATR) spectra and X-ray photoelectron spectroscopy (XPS) showed that the resulting plasma film containing amine and amide was about 0.5 mum thick. The ion selectivity coefficient for Ht of the plasma modified Nafion(R) membrane was measured and the results showed that a linear Nernst response was exhibited and the selectivity of proton was enhanced. The resistance of modified Nafion was only slightly higher than that of the Nafion(R) membrane.