The wetting characteristics of an amorphous poly(ethylene terephthalate) (PET) film by water were studied by the Wilhelmy plate technique in the dynamic and static modes. At room temperature, a dynamic hysteresis of 40 degrees (theta(A) = 80 degrees, theta(R) = 40 degrees) was found. It was interpreted in terms of water adsorption-desorption phenomena. The air-water and water-air equilibration processes of the PET surface were studied. The static mode was most useful for this purpose. It showed that it takes about 10 days to reach equilibrium at 20 degrees C and that equilibration with water is only partially reversible. Surface restructuration was described by molecular modelling. The validity of this description was confirmed by a good quantitative agreement between experimental and calculated data. An increase of the temperature accelerates molecular rearrangements especially around the glass transition temperature of the polymer.