Poly(5-aminoquinoline) films (10 to 400nm) were prepared on gold electrodes by anodic polymerization in acetonitrile using cyclic voltammetry and potential step methods. The films were found to be smooth, homogeneous and adherent. The electrochemical quartz crystal microbalance and ellipsometric measurements proved that the polymer film thickness increases linearly with increasing anodic charge of formation. The electroactivity of the polymer films was found to be very small in acetonitrile and aqueous solutions. The impedance measurements indicated that the polymer films are very resistive, with a resistivity of approximately 0.4 M Omega cm. In sulphuric acid solutions, capacity- and photocurrent-potential curves of the polymer films show semiconducting behaviour. XPS and FT-IR indicated the presence of perchlorate anions in the polymer films as well as in the isolated product of the constant potential electrolysis. It is proposed that the polymerization proceeds mainly via coupling at position 1 (leading to quaternary ammonium cation formation) and at position 8. The exchange of the counter anions with [Fe(CN)(6)](4-) anions from neutral solutions was found to be about 10% to 18% of the total inserted anions. With a loading efficiency of about 0.15 mol l(-1), poly(5-aminoquinoline) films can find applications in the field of fixed-mediators.