The invention relates to a process for the preparation of water-soluble polymers containing polyalkylene glycol ether side chains and having molecular weights of from 15,000 to 65,000 by solution polymerization of esters of ethylenically unsaturated carboxylic acids and polyalkylene glycols which are masked on the end groups at one end, if desired together with another monomer in at least one hydrocarbon at monomer concentrations of from 70 to 95% by weight in the presence of free-radical-forming polymerization initiators and, if desired, polymerization regulators at temperatures of up to 200° C., removal of the solvent used in the solution polymerization, and dissolution of the polymers in water to give from 50 to 80% strength by weight solutions, with polymers containing acid groups being neutralized if desired.