Poly (methyl red) film was deposited on a carbon paste electrode (CPE) through cyclic voltammetry (CV) and a novel and simple biosensor (PMR/CPE) for highly sensitive and selective determination of dopamine (DA) was fabricated. The polymer film was characterized by scanning electron microscopy (SEM) and the electrochemical behavior of DA at PMR/CPE was studied. It was illustrated that the polymer film had excellent electrochemical catalytic activity towards DA. The anodic peak current of DA was dramatically enhanced by about four folds at PMR/CPE and the standard rate constant (Ks) for DA could be calculated to be 4.686 s(-1). Moreover, the separation of oxidation peak potentials of DA and uric acid (UA) was 140 mV, and no oxidation peak for ascorbic acid (AA) appeared at PMR/CPE. Thus, the sensitive and selective determination of DA was carried out successfully. The linear response was obtained over two concentration internals: 1.00 x 10(-8)similar to 1.00 x 10(-7) mol L-1 and 1.00 x 10(-7)similar to 1.00 x 10(-3) mol L-1 with a low detection limit (S/N = 3) of 5 x 10(-9) mol L-1. With favorable selectivity and sensitivity, the present method has been successfully applied to the determination of DA in pharmaceutical samples. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.042202jes] All rights reserved.