A method of bonding two substrates at least one of which is a rubbery polymeric material having carbon-carbon double bonds on the polymer backbone, the method comprising: a) applying an aqueous polyurethane dispersion adhesive composition to at least one of the substrates, the adhesive compostion further comprising an epoxy resin; b) allowing the composition to dry; and then c) joining the substrates with heating to activate the adhesive. The substrates are suitably footwear materials such as a molded rubber outer sole which has been first primed with a chlorinating primer, and a foam midsole of a material such as a lightly crosslinked ethylene vinyl acetate. The process results in bonded assemblies having improved humidity resistance.