A new type of amperometric phenol biosensor based on chitosan/layered double hydroxides organic-inorganic composite film was described. This hybrid material combined the advantages of organic biopolymer, chitosan, and inorganic layered double hydroxides. Polyphenol oxidase (PPO) immobilized in the material maintained its activity well as the usage of glutaraldehyde was avoided. The composite films have been characterized by Fourier transform infrared. The results indicated that PPO retained the essential feature of its native structure in the composite film. The enzyme electrode provided a linear response to catechol over a concentration range of 3.6 x 10(-9) to 4 x 10(-5) M with a sensitivity of 2750 +/- 52 mA M-1 cm(-2) and a detection limit of 0.36 nM based on S/N = 3. The apparent Michaelis-Menten constant (K-M(app)) for the sensor was found to be 0.13 mM. The activation energy for enzymatic reaction was calculated to be 27.6 kJ mol(-1). Furthermore, the biosensor exhibited excellent long-term stability and satisfactory reproducibility.