The interactions of two high molecular weight polycarboxylic ligands [polyacrylic-co-maleic, MW = 70 kDa, and poly(methyl vinyl ether-co-maleic acid), MW = 15 kDa] with some polyamines [1,4-diaminobutane (or putrescine), histamine and poly(allyl)amine, MW = 15 kDa] were studied, at t = 25 °C and at low ionic strength (I = 0.015 mol L -1 ) by potentiometric measurements. For all investigated systems, the formation of (am)(L)H i species was found (am = amine, L = polycarboxylic ligand, i = 1…4); the stability of polyammonium-polycarboxylate complexes is fairly high and the formation percentage of most species reaches ∼ 90% in the experimental conditions (mmolar concentration of reactants). The dependence on temperature and ionic strength of the stability of polyamine-polycarboxylate species was studied using some semiempirical equations and enthalpy data for the protonation of both components. The sequestering ability of polyelectrolytes towards amines was modeled by a sigmoid Boltzman type equation and was defined by calculating the parameter pL 50 (the total ligand concentration, aslog C L , able to bind 50% of cation); this parameter gives an objective representation of this ability. The dependence of pL 50 on pH, ionic strength and temperature was studied too.