Alkoxysilyl-terminated prepolymers in which the alkoxysilyl group is linked to a tertiary nitrogen group through a Cl carbon spacer exhibit excellent moisture curing reactivity and yet are easily prepared. The tertiary nitrogen group-containing .alpha.-aminoalkoxysilyl group is introduced into the prepolymer by reacting a tertiary nitrogen group-containing .alpha.-aminoalkoxysilane with an isocyanate-terminated prepolymer or isocyanate-functional precursor thereof.