Abstract: This invention is directed to a polyurethane mixture. More particularly, there is provided a mixture polyurethanes comprising a first polyurethane with at least two end groups, where each end group comprises a terminal isocyanate and a polyether; a second polyurethane with at least two end groups, where each end group comprises a terminal isocyanate group and a non-functional group; and a third polyurethane with at least two end groups, where one end group comprises a terminal isocyanate and a polyether and one other end group comprises a terminal isocyanate and a non-functional group. A method for improving the sag resistance of an aqueous composition is also provided. This method permits the formulation of aqueous compositions which resist the tendency to sag. The polyurethane mixture of this invention is useful for thickening aqueous compositions such as paints, coatings, cosmetics, personal care items, hair shampoos and conditioners, cleaners, and the like.