An adhesive system for preparing lignocellulosic composites comprising: a) an aqueous primer composition; and, b) a polyurethane adhesive composition, wherein said aqueous primer composition comprises: up to 10 wt.%, by weight of the composition, of surfactant selected from the group consisting of water-soluble surfactants, water emulsifiable surfactants and mixtures thereof; and, from 0 to 25 wt.%, by weight of the composition, of polyol selected from the group consisting of water-soluble polyols, water dispersible polyols, water emulsifiable polyols and mixtures thereof, wherein said polyols have a molecular weight less than 5000 daltons, with the proviso that the aqueous primer composition must comprise at least one of said polyol or a surfactant having hydroxyl functionality and a molecular weight less than 5000 daltons, wherein said surfactant of the primer composition is selected from the group consisting of: siloxanebased surfactants; alkyl polyglucosides; alkoxylated fatty acids; alkoxylated alcohols; alkylsufosuccinates; acetylenic diols; and, mixtures thereof and wherein said polyurethane adhesive composition is a moisture-curable, one-component polyurethane adhesive composition and wherein the one-component polyurethane adhesive composition comprises: a prepolymer having free NCO groups, said prepolymer being obtainable from at least one component A comprising a compound reactive toward isocyanates and at least one component B comprising an isocyanate; from 0 to 40% by weight of filler; from 0 to 20% by weight of customary additives and assistants; and from 0 to 20% by weight of an activator; wherein said prepolymer having free NCO groups being characterized by: i) an NCO content of from 5 to 30%, preferably from 10 to 25% by weight, based on the prepolymer; ii) a functionality of from 2.2 to 3, preferably from 2.4 to 2.9; and, iii) a viscosity at 20°C of from 300 to 35,000 mPas, preferably from 1000 to 10,000 mPas. a) an aqueous primer composition; and, b) a polyurethane adhesive composition, up to 10 wt.%, by weight of the composition, of surfactant selected from the group consisting of water-soluble surfactants, water emulsifiable surfactants and mixtures thereof; and, from 0 to 25 wt.%, by weight of the composition, of polyol selected from the group consisting of water-soluble polyols, water dispersible polyols, water emulsifiable polyols and mixtures thereof, wherein said polyols have a molecular weight less than 5000 daltons, with the proviso that the aqueous primer composition must comprise at least one of said polyol or a surfactant having hydroxyl functionality and a molecular weight less than 5000 daltons, a prepolymer having free NCO groups, said prepolymer being obtainable from at least one component A comprising a compound reactive toward isocyanates and at least one component B comprising an isocyanate; from 0 to 40% by weight of filler; from 0 to 20% by weight of customary additives and assistants; and from 0 to 20% by weight of an activator; i) an NCO content of from 5 to 30%, preferably from 10 to 25% by weight, based on the prepolymer; ii) a functionality of from 2.2 to 3, preferably from 2.4 to 2.9; and, iii) a viscosity at 20°C of from 300 to 35,000 mPas, preferably from 1000 to 10,000 mPas.