The influence of moisture on the dielectric properties of poly(ethylene-co-vinyl alcohol) copolymer (EVA) has been investigated using a Seiko DES 100 dielectric spectrometer between 170 and 385 K in the frequency range 10-100 kHz. A scanning rate of 1 K min(-1) was used. Two peaks were observed. The a-relaxation is ascribed to the glass transition. The presence of water facilitates molecular motion, shifting the a-relaxation to lower temperatures. The beta-relaxation is due to the local-mode relaxation in the crystalline regions of the copolymer or to the motion of hydroxyl groups. At low temperatures, water molecules may form mechanically stable bridges between the vinyl alcohol regions of the copolymer chains which inhibit molecular motion.