The invention relates to a polyether urethane of the general formula ##STR1## wherein R.sup.1 denotes H or an alkyd (sic) radical of 1 to 8 carbon atoms,R.sup.2 denotes an alkylene radical of 2 to 10 carbon atoms or a cycloalkylene radical of 6 to 20 carbon atoms or an arylene radical of 6 to 20 carbon atoms,R.sup.3, R.sup.4 denote an optionally substituted alkyl radical of 1 to 8 carbon atoms or a joint ring whose members are R.sup.3 and R.sup.4,n denotes 2 to 1800m denotes 1 to 15.The invention further relates to a process for its preparation, to a flow-out agent for water-borne paints and to the use of the polyether urethanes as flow-out agents in water-borne, cathodically depositable electro-coating paints.