A polyaniline-poly(3-methylthiophene)-poly(3,3 '-diaminobenzidine) film was deposited on a platinum disc electrode in dichloromethane containing tetrabuthylammonium perchlorate supporting electrolyte and used for the amperometric determination of dopamine. At a pH of 2.0, this electrode allowed successful determination at a lower potential than the oxidation potential of dopamine. The limit of detection, limit of quantification, and the linear dynamic range were determined to be 1.63x10(-5)mM, 5.43x10(-5)mM and 5.43x10(-5) to 100.0mM (R-2=0.997), respectively. The reproducibility was investigated by using three different films and good analytical results were obtained. In addition, the modified electrode was successfully employed to determine dopamine in human serum with good recoveries.