Functionalized poly N,N-dimethylaniline film was prepared by adsorption of ferrocyanide onto the polymer forming at the surface of carbon paste electrode (CPE) in aqueous solution. The electrocatalytic ability of poly N,N-dimethylaniline/ferrocyanide film modified carbon paste electrode (PDMA/FMCPE) was demonstrated by oxidation of L-cysteine Cyclic voltammetry and chronoamperometry techniques were used to investigate this ability In the optimum pH (6 00), the electrocatalytic ability about 480 mV and the catalytic reaction rate constant, (k(h)), can be seen 3.08 x 10(3) M(-1) s(-1). The catalytic oxidation peak Current determined by cyclic voltammetry method was linearly dependent on the L-cysteine concentration and the linearity range obtained was 8.00 x 10(-5) -2.25 x 10(-3) M. Detection limit of this method was determined as 6.17 x 10(-5) M (2 sigma). At a fixed potential under hydrodynamic conditions (stirred solution), the calibration plot was linear over the L-cysteine concentration range 7.40 x 10(-6) M-1.38 x 10(-4) M. The detection limit of the method was 6.38 x 10-6 M (2 sigma) (C) 2009 Elsevier B.V. All rights reserved.