An experimental investigation was carried out to study the effect of different surface treatments on the moisture absorption behavior of glass fabric /polyester composites. The materials under study included composites containing clean glass fabrics, fabrics treated with a silane coupling agent, and fabrics coated with a poly(dimethylsiloxane) elastomer. Weight gain data versus time of immersion were collected at three immersion temperatures and water uptake at equilibrium as well as apparent diffusion coefficients were calculated. The interlaminar shear strength was also measured at the initial dry state and at different stages of the absorption process to estimate the interfacial contribution to sorption behavior. (c) 2005 Wiley Periodicals, Inc.