Chitosan membranes with various degrees of deacetylation and different molecular weights (MW) were prepared by film casting with aqueous solutions of chitosan and acetic acid. Ultraviolet (UV) spectrometry and infrared (IR) spectrometry were used to determine the degree of deacetylation (DDA) of chitosan. The viscosity-average MW of chitosan was measured in an aqueous solvent system of 0.25 M CH3COOH/0.25 M CH3COONa. The intrinsic ionic conductivities of the hydrated chitosan membranes were investigated using impedance spectroscopy. It was found that the intrinsic ionic conductivity was as high as 10(-4) S cm(-1) after hydration for 1 h. The tensile strength and breaking elongation of the membranes were evaluated according to standard ASTM methods. The crystallinity and swelling ratio of the membranes were examined. A tentative mechanism for the ionic conductivity of chitosan membranes is also suggested.