A self-propagating association of zwitterionic polymers is observed when a small amount of x,y-ionene bromide (x=3 or 6; y=3, 4, 6, 10 or 12) polymer is added to aqueous solution of zwitterionic polymer, poly[3-dimethyl(methacryloyloxyethyl)ammoniumpropanesulfonate] (PDMAPS), to give large amount of PDMAPS precipitate. The self-propagating association initiated by ionene polymers is explained in terms of the electrostatic interaction between the ionene polymers and the zwitterionic polymers whereupon the geometry of the charges on the polymer chains plays an important role.