The effect of choline oxidase (Chox) on the electrochemical polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT) was described. Result shows that the growth rate of PEDOT film varied with the addition of Chox quantity. The properties of PEDOT and PEDOT/Chox films were characterized by XPS and UV-vis absorption techniques. Meanwhile, a novel UV-vis absorbance method for the detection of choline was achieved. In a medium of 1/30 M phosphate buffer solution ( pH 8.0), a very sensitive absorbance peak at 293 nm was observed. The linear relationship between UV-vis absorption intensity and choline concentration in a range from 1.0 x 10 (6) to 5.1 x 10 (5) M was obtained. This method has also been applied to determine choline in several feedstuff additive samples. (c) 2008 Elsevier B.V. All rights reserved.