Abstract: High molecular weight polyphenylene ethers are prepared from a monohydric phenol by an oxidative coupling reaction with oxygen in the presence of a catalyst complex obtained from a copper salt and an organic amine, and in the presence of a solvent, by a process in which the metal component of the catalyst is removed after the polymerization by adding one or more organic ammonium salts of the general formula ##STR1## where A.sup..crclbar. is an anion or polyanion of an organic carboxylic, sulfonic or phosphonic acid, R.sup.1 is hydrogen, R.sup.2 and R.sup.3 are each hydrogen, alkyl of 1 to 18 carbon atoms or aryl and R.sup.4 is alkyl of 1 to 18 carbon atoms or aryl.