The electrochemical behaviour of the copper-thallium composite film has been investigated in 10 mM NaOH solutions towards the electroreduction of nitrate and nitrite ions in the range of potentials between 0.0 and -1.4 V vs. SCE. The Cu45Tl55 binary films exhibited a higher electrocatalytic activity for the reduction of NO3- and NO2- than pure copper and thallium electrodeposited films. The presence of thallium species in the composite film causes a marked increase of the roughness factor with subsequent increase of the catalytic response due to the nitrate and nitrite reduction. Alternatively, thallium particles act as promoters of NO3- and NO2- adsorption on the electrode surface with their subsequent accumulation on the surface catalytic centres and increase of the cathodic currents. Under pulsed chronoamperometric detection (PCD) using a selected waveform of potentials of 0.0 V (E-ads) for 200 ms (t(ads)) and -1.3 V (E-det) for 400 ms (t(det)), the Cu45Tl55 composite electrode exhibits interesting cathodic currents upon nitrate and nitrite addition. The detection limits (S/N = 2), evaluated in PCD conditions for nitrate and nitrite ions were 190 and 250 muM, respectively. (C) 2004 Elsevier B.V. All rights reserved.