A glassy carbon electrode modified with CeO2 nanoparticles was constructed and was characterized by electrochemical impedance spectrum (EIS) and cyclic voltammetry (CV). The resulting CeO2 nanoparticles modified glassy carbon electrode (CeO2 NP/GC electrode) was used to detect uric acid (UA) and ascorbic acid (AA) simultaneously in mixture. This modified electrode exhibits potent and persistent electron-mediating behavior followed by well-separated oxidation peaks towards UA and AA with activation overpotential. For UA and AA in mixture, one can well separate from the other with a potential difference of 273 mV, which was large enough to allow the determination of one in presence of the other. The DPV peak currents obtained in mixture increased linearly on the UA and AA in the range of 5.0 x 10(-6) to 1.0 X 10(-3) mol/L and 1.0 x 10(-6) to 5.0 x 10(-4) mol/L, with the detection limit (signal-to-noise ratio was 3) for UA and AA were 2.0 x 10(-7) and 5.0 x 10(-6) mol/L, respectively. The proposed method showed excellent selectivity and stability, and the determination of UA and AA simultaneously in serum was satisfactory. (c) 2006 Elsevier Ltd. All rights reserved.