Abstract: Adhesion of an epoxy resin to glass has been investigated by fracture mechanics test.Specimens were tested after various times of immersion in water at 80℃, and the adhesive failure energy 6 determined as a function of crack velocity. The effects of adding silane coupling agents to the epoxy resin, and the influence pH of water were studied.Using the generalized fracture mechanics theory, an intrinsic adhesive failure energy θ₀ which is defined as the energy required to break interatomic bonds across unit area of the interface were separated from 9, The θ₀ value of dry sample, 7.25Jm^-2, is approximately 24 times the expected Van der waals interaction energy and this suggests that at least some of the bonds between epoxy resin and glass are primary.