Two hyperbranched chelating polymers, glucoheptonamide derivatives of dendrimeric poly(amido amine) and poly(ethylene imine), were employed in polymer-assisted ultrafiltration and concentration of boron from aqueous feed streams. For feeds ocontaining approximately 1 mM B (10 ppm), volume reduction factors of 20 were observed in cyclic adsorption-desorption. The concentrations of both polymers declined due to permeation through,an ultrafiltration membrane with pore sizes which should have retained them. Acid-catalyzed hydrolysis of the amide linkages between the polymer backbone and the chelating side groups is implicated in this loss of polymer mass and effectiveness.