In order to reduce methanol cross-over to the positive electrode in a direct-methanol fuel cell (DMFC), the concept of modifying the morphology of the proton-conducting membrane is proposed. The method involves using plasma etching and palladium-sputtering on a Nafion (TM) polymer membrane. Methanol permeability tests were conducted in a specially-designed cell. Plasma etching of Nafion (TM) membrane increases the roughness of the membrane surface and decreases the methanol permeability. The sputtering of palladium on the plasma-etched Nafion (TM) further decreases the methanol cross-over. Improved DMFC performance curves are obtained in a single cell which contains the modified Nafion (TM). (C), 2001 Elsevier Science B.V. All rights reserved.