Voltammetric determination of 4-nitrophenol (4-NP) has been carried out on graphite nanoflakes (GNFs) modified glassy carbon electrode (GCE) (GNFs/GCE). The GNFs were easily prepared by paired electrolysis of graphite rods in a blank solution of NaOH. In comparison with GCE, the GNFs/GCE showed higher electrocatalytic activity (positive shift of peak potential and onset potential) toward the 4-NP reduction. Under the optimized conditions, the oxidation peak currents varied linearly with a concentration range for 4-NP of 1-6000 mu M (over three consecutive calibration curves) with a detection limit of 0.7 mu M (3 s/slope) and quantification limit of 2.3 mu M (10 s/slope). The proposed method exhibited several advantages including easy fabrication, low cost, good sensitivity, high stability, good reproducibility, high selectivity and very broad linear range, and was successfully applied to detect 4-NP in water samples with satisfied results. (C) 2014 The Electrochemical Society. All rights reserved.