Abstract: The invention provides cross-linkable polymer powder compositions containing a) at least one water-soluble polyhydroxy compound; b) at least one boric acid complex compound which is of limited solubility in water that is, it has a water solubility of less than 10 g per liter at normal conditions; and optionally c) a water-soluble film-forming polymer consisting of one or more free-radical polymerizable, ethylenically unsaturated monomers. The compositions are useful as a constituent in adhesives, plaster, jointing mortars, paints and binders for coating compositions, textiles, paper and the like.