Plasma surface-treatment of silk and cotton fabrics were carried out in a hexafluoropropene (C3F6) atmosphere under different experimental conditions. Analysis of the treated fibers by X-ray photoelectron spectroscopy (XPS) indicated about 50 at% fluorine atoms were incorporated in the surface structure of two fibers and confirmed the presence of -CF, -CF2, -CF3 groups on the surface. After water-washing and alcoholextraction, though partial loss of fluorine from the surface has been observed, contact angle and wet-out time measurements on the fibers still show much improved hydrophobic properties. The other properties of the treated fabrics, such as water vapor permeability and tensile strength were also evaluated. (c) 2006 Elsevier B.V. All rights reserved.