A novel ECR-modified electrode is fabricated by electrodeposition of Eriochrome Cyanine R (ECR) at a glassy carbon (GC) electrode by cyclic voltammetry (CV) in double-distilled water. The characterization of the ECR film modified electrode is carried out by atomic force microscopy (AFM), infrared spectra (IR), spectroelectrochemistry and cyclic voltammetry. The results show that a slightly heterogeneous film formed on the Surface of the modified electrode, and the calculated Surface concentration of ECR is 2 x 10(-10) mol/cm(-2). The ECR film modified GC electrode shows excellent electrocatalytic activities toward the oxidation of serotonin (5-HT) and norepinephrine (NE). Furthermore, the modified electrode can separately detect 5-HT and NE, even in the presence of 200-fold concentration of ascorbic acid (AA) and 25-fold concentration of uric acid (UA). Using differential Pulse voltammetry (DPV). the peak currents of 5-HT and NE recorded in pH 7 solution are linearly dependent on their concentrations in the range of 0.05-5 mu M and 2-50 mu M, respectively. The limits of detection are 0.05 and 1.5 mu M for 5-HT and NE, respectively. The ECR film modified electrode can be stored stable for at least 1 week in 0.05 M PBS (pH 7) at 4 degrees C in a refrigerator. Owing to its excellent selectivity and sensitivity. the modified electrode could provide a promising tool for the simultaneous determination of 5-HT and NE in complex biosamples. (C) 2009 Elsevier Ltd. All rights reserved.