Aqueous dispersions of polyurethanes consisting of(a) organic polyisocyanates,(b) polyesterpolyols having a molecular weight of from 500 to 5,000,(c) organic hydroxy compounds having a molecular weight of from 62 to 400 and two terminal groups which are reactive to isocyanate groups, as chain extenders, and(d) compounds containing ionic groups or groups which can be converted to ionic groups and one or more isocyanate groups or a hydroxyl or amino group which is reactive to isocyanate groups,which contain from 0.05 to 2 meq of ionic groups incorporated into the polyurethane via (d) per g of polyurethane are particularly suitable for adhesives when the chain extenders (c) are incorporated in an amount of from 1.5 to 8 moles per mole of polyols, and a minor amount of (a) can be replaced with monoisocyanates, and a minor amount of (b) with polyetherpolyols.