Thermo-stimulated creep analysis is performed to characterize the effect of water on the anelastic properties of the model system : epoxy resin-glass beads. The changeable parameter is the nature of the interfacial region. The behaviour of filled composites after water exposure is compared for composites filled with raw beads, beads treated with silane coupling agent, and beads coated with elastomeric adduct (tailoring interphase). Both the glassy region and the glass transition region are investigated. Specific behaviours are reported in the case of epoxy reinforced with silane-treated beads and coated beads.