In this study, the boron-doped diamond (BDD) electrode using Ti as a substrate (Ti/BDD) was applied to oxidize Orange II anodically. The effects of operational variables on the process performance were examined systematically. Experimental results showed that high pH, high temperature and low current density were beneficial for Orange II oxidation. Nevertheless, the pH effect was not significant. There was no effect of the electrolyte concentration on oxidation efficiency in the investigated range of 1500-3000 mg/L Na2SO4. In addition, it was observed that polymeric intermediate products were formed during oxidation. The amount of the polymeric products depended on operational conditions. High pH, high temperature, low current density and low initial Orange II concentration tended to suppress the formation of polymeric products. (C) 2005 Elsevier B.V. All rights reserved.