Improved process for making polyether polyols.

Process for the production of polyether polyols by polyaddition of alkylene oxides to starter compounds containing active hydrogen atoms in the presence of double metal cyanide catalysts, wherein during or after the polyaddition reaction the reaction mixture 1 is conducted 1000 times through a zone having an energy density of at least 5 x 106 J / m3, rising the residence time of the reaction mixture by passing at least 10-6 seconds.