The electrochemical behaviors of dioxygen (O-2) were studied by using rotate ring-disk electrode (RRDE) and other bare glassy carbon electrode (GCE) and single-waited carbon nanotubes (SWNTs)-dihexadecyl hydrogen phosphate (DHP) film modified GCE. The results showed that the electrochemical reduction of dioxygen was considered to proceed by a two-step two-electron reduction pathway at both bare GCE and SWNTs-DHP film modified GCE in 0.1 mol/L air-saturated sodium hydroxide (NaOH). Maybe because each reaction rate for two cases was different the cyclic voltammograms measurements exhibited different behaviors. The detection of ring current confirmed the presence of middle product hydrogen peroxide (H2O2). Furthermore, larger current and more positive reduction potential indicated that SWNTs showed a catalytic effect towards the electrochemical reduction of dioxygen. (c) 2005 Elsevier Ltd. All rights reserved.