This work reports the formation of water-repellent surface on polyethyleneterephthalate (PET) fiber via plasma polymerization at atmospheric pressure. PET fiber was treated by employing a radio frequency (RF) plasma In a mixture of argon gas and gas-phase hexamethyldisiloxane (HMDSO). The surface morphologies and the chemical functional groups of plasma-treated fibers were characterized by a scanning electron microscopy, a Fourier transform infrared spectrometry, and an energy dispersive spectrometer. The water repellency was also characterized by comparing with American Association of Textile Chemists and Colorists (AATCC) standard spray test chart. (C) 2008 Elsevier B.V. All rights reserved.