Electropolymerization of new fuchsin produces two types of stable and electrochemically active films in strong and weak acidic aqueous solutions. These films can be produced on glassy carbon, platinum, gold, and transparent semiconductor tin oxide electrodes. An electrochemical quartz crystal microbalance and cyclic voltammetry were used to study the in situ growth of poly (new fuchsin) films. New fuchsin is a molecule that has three branched monomers, and its polymerization forms a dendrimer. The polymer films showed redox couples, and when transferred to various acidic to weak basic aqueous solutions, the formal potential versus pH plot had a slope of -60 mV pH(-1). The electrocatalytic reduction of HNO2 by poly (neutral red) in a strong acidic aqueous solution showed obvious electrocatalytic reduction activity. A modified electrode containing a hybrid of two organic films was also prepared from poly (new fuchsin) and poly (neutral red) films. The two films, with a formal potential difference of about 0.6 V, were both electrocatalytically active for IO3- oxidation, but produced different products in strongly acidic aqueous solution. The electrocatalytic reduction of BrO3 was achieved only by poly (neutral red) in a strongly acidic aqueous solution. The polymer films also reduced SO52-, IO4- and Cr2O72- electrocatalytically, and oxidized ascorbic acid electrocatalytically in aqueous solution. (C) 2003 Elsevier Science B.V. All rights reserved.