A sensor for acetylcholine/choline is described using a tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) electrode modified with acetylcholine esterase (AChE) and choline oxidase (ChO) enzymes. DC cyclic voltammetry and impedance measurements of the enzyme-modified TTF-TCNQ electrode that indicate the regeneration of choline oxidase at the electrode surface are reported. Effective electrochemical rate constants for the present enzyme electrode are calculated using the expressions derived by Albery et al. (1), which show the enzyme kinetics as the rate-limiting step. The values of the effective electrochemical rate constants are close to those reported by Hale and Wightman (2). The application of the sensor is described for the determination of fluorode ion and nicotine based on the reversible inhibition of AChE activity. The range of detection of fluoride ion and nicotine is found to be 5×10-6 to 5×10-4M.