The protonation and coordinating ability of a series of poly(amido-amine)s towards heavy and alkaline-earth-metal ions has been studied in aqueous media (0.1M NaCI and 25°C) and reviewed for their potential application in the treatment of metal-containing waste waters, when in cross-linked and/or silica-grafted forms. Transition metal ions [Cu(II), Zn(II), Fe(III)] covalently coordinated two basic nitrogens of each monomer unit, and different complex species formed in different range of pHs. As further binding sites for metal ions, peptide linkages of the polymer displayed a stoichiometric deprotonation. The alkaline-earth Ca(II) ion showed electrostatic coordination with carboxylate anions; any increase in the number of the latter reflected greater complexing stability. Stability constant (log β) values showed the selective chelation towards metal ions.