Optically active poly[(R)- or (S)-1,4-bis(2-(3',4'-ethylenedioxy)thienyl)-2-benzoic acid 1-methylheptyl ester] was prepared by an electrochemical technique and characterized by circular dichroism measurements. It was found that the optical activity and optical rotation of the film could be controlled by adjusting the electronic state of the electrochemical process. Polymer films prepared in the oxidized state exhibit weak Cotton effect, while the reduced polymer film exhibits the expected mirror-image bisignate Cotton effect in the region of the pi-pi* transition of the polmer main chain. These results indicate that the main chain itself is chiral in the film state. This procedure has great potential for the preparation of functional electrochromic devices based on the good film-forming properties of the chiral polymer.