A glassy carbon electrode modified with the composite film of MnO2 and Nafion was used for the sensitive voltammetric determination of epinephrine (EP) and the modified electrode exhibited excellent electrocatalytic activity to EP. MnO2 in various structural forms has shown superior electrochemical performance, high pseudocapacitance along with the cost-effective and environment friendly nature and thus attracting enormous attention. The electrochemical response characteristics of the modified electrode toward EP were investigated by cyclic voltammetry and differential pulse voltammetry. Under the optimum conditions, the cathodic peak current increases linearly with increasing EP concentration in the ranges of 0.03-10 mu M and 10-100 mu M, with the correlation coefficient of 0.999 and 0.993, respectively. The sensitivity of the modified electrode is calculated to be 5775 mu A mM(-1) cm(-2) and the detection limit is 0.005 mu M (based on the S/N = 3). The measurement repeatability of the MnO2/Nafion/GCE was examined with the same electrode and the relative standard deviation (RSD) was 0.86% for seven successive assays. Three modified electrodes showed an acceptable reproducibility with RSD of 1.13% for amperometric determination at 100 mu M EP. The interferences of some metal ions and organic compounds have been investigated by cyclic voltammetry. The modified electrode can be used for the determination of EP in practical injection. (C) 2011 Elsevier B.V. All rights reserved.