Poly(tetrafluoroethylene) and a fluoroethylene copolymer were surface treated with a 2.45-GHz microwave plasma to enhance their adhesion to a vinylester thermoset. The plasmas were generated with an inert gas (Ar) and with reactive gases (H-2, O-2, and N-2). The lap-joint shear stress was measured on fluoropolymer samples glued with the vinylester. In general, the stress at failure increased with increasing plasma-energy dose. The H, plasma yielded the best adhesion, and X-ray photoelectron spectroscopy revealed that it yielded the highest degree of defluorination of the fluoropolymer surface. The defluorination efficiency declined in the order H-2, Ar, O-2, and N-2. Contact angle measurements and scanning electron microscopy revealed that the surface roughness of the fluoropolymer depended on the rate of achieving the target energy dose. High power led to a smoother surface, probably because of a greater increase in temperature and partial melting. (c) 2005 Wiley Periodicals, Inc.