We report here the first electrochemical pathway to prepare Au- and Ag-containing bimetallic nanocomplexes with a mean diameter of 5 nm in 0.1 M HCl aqueous solutions without addition of any stabilizer. First, a silver substrate was roughened by a triangular-wave oxidation-reduction cycle (ORC) in an aqueous solution containing 0.1 M HCl. Silver-containing complexes were left in the solution after the ORC treatment. Then a gold substrate was subsequently roughened by the similar ORC treatment in this solution. Encouragingly, polypyrrole (PPy)-coated Au and Ag bimetallic nanocomposites with a nanorod structure and a diameter smaller than 15 nm can be prepared by the formation of self-assembled monolayers and orderly autopolymerization of pyrrole monomers on these bimetallic nanocomplexes, and further link them together. (c) 2004 Elsevier Ltd. All rights reserved.