For the preparation of elastic flexible polyurethane foams with improved breaking elongation and very good setting behavior as well as densities from 7 to 120 grams per liter, organic polyisocyanates are reacted in the presence of blowing agents, catalysts and, optionally, auxiliaries and/or additives with polyols based on polyoxyalkylene polyols having terminal oxyethylene blocks of a degree of oxyethylation of 1 to 13 and which have a content of primary hydroxyl groups at the corresponding degree of oxyethylation equal or exceeding the value of curve A in the Figure in which curve A describing the relationship of the content of primary hydroxyl groups with the degree of oxyethylation.