The surface of indium-tin oxide (ITO) substrates was successfully modified with aziridine. Modification of the surface was achieved through facile ring-opening, and hyperbranching polymerization of the ring-strained heterocycle initiated from the reactive group on the surface. Amine density of the aziridine-modified ITO measured with UV-vis spectrophotometry is 10 amines/nm(2). Cyclic voltammetric analysis showed that the aziridine-modified electrode was less active for Ru(NH3)(6)(3+) in comparison with the pristine electrode, while no difference was observed for Fe(CN)(6)(4-). Electrochemical impedance spectroscopic experiments unveiled that the modified electrode was more efficient for electron transfer to the latter species than to the former. (C) 2004 Published by Elsevier Inc.