The sensitivity of poly(1,8-diaminonaphthalene) [poly(1,8-DAN)] to heavy metal ions (Ag+, Hg2+, Cu2+) was studied by means of electrochemical (open circuit potential (ocp), cyclic voltammetry) and spectroscopic methods (IR, Raman spectra). Changes of the open circuit potential of the polymer electrode indicate that Ag+ and Hg2+ ions are able to oxidise poly(1,8-DAN), while Cu2+ ions do not influence the ocp of the polymer. Cyclic voltammograms of poly(1,8-DAN) give direct evidence that Ag+ ions are reduced at the polymer surface whereas Hg2+ or Hg-2(2+) ions are bonded by the polymer matrix. IR and Raman spectra indicate that Cu2+ and Hg2+ or Hg-2(2+) ions are complexed by the amino groups of the polymer.