Abstract: The subject of the invention is a process for the manufacture of polycondensation products from hydroxymethylphosphonium compounds, characterized in that at least one anhydrous tetrakis-(hydroxymethyl)-phosphonium salt or tetrakis-(hydroxymethyl)-phosphonium hydroxide is condensed with itself in an anhydrous medium, optionally using an acid catalyst and optionally in the presence of at least one inert organic solvent, at 100.degree. to 150.degree. C, preferably 120.degree. to 150.degree. C, the condensation being continued until 0.5 to 1.5 mols of water have been eliminated per 1 mol of phosphonium compound employed, free hydroxyl groups are, if appropriate, at least partially etherified with at least one alkanol with 1 to 4 carbon atoms, and that the salt of the polycondensation products are, where relevant, converted into the corresponding hydroxides.The polycondensation products are used for the flameproofing of organic fibre material, especially textiles.