The role played by sorbed water molecules present within poly(ethylene terephthalate) film at the moment of uniaxial. drawing on the appearance and the percentage of the strain-induced crystalline (SIC) phase is investigated by birefringence, X-ray diffraction, and differential scanning calorimetry measurements. We show that, for law draw ratio, water play its traditional plasticizer effects. The SIC phase appears for a draw ratio, which depends weakly on the relative humidity. The water does not modify the degree of crystallinity of drawn films but, impedes the growth of a part of the crystallites and modify their crystalline size. For high draw ratio, water impedes the orientation of the amorphous phase.