Electrolytic cells for electrochemical oxygen demand (ECOD) measurements based on total electrolytic decomposition at a boron-doped diamond (BDD) electrode were developed for rapid measurement of organic pollutants at low concentrations. Using improved electrolytic cells designed for efficient mass transfer, the ECOD for 10 mu M potassium hydrogen phthalate (theoretical ECOD: 2.3 mg-O-2 L-1) was determined in a relatively short electrolysis time. Thus, ECOD measurements using these cells would be useful for estimating organic water pollution in industrial waste and lake water.