Treatment of poly(2-methoxyaniline-5-sulfonic acid) (PAS) with LiOH gave its lithium salts, PAS(Li)s, with various degrees of lithium sulfonation. Structure of a fully lithium-sulfonated PAS(Li) was determined by H-1 NMR spectroscopy and elemental analysis. Cyclic voltammetry and complex impedance analysis revealed electrochemical properties of the PAS(Li) films depending on the degree of the lithium sulfonation. PAS(Li)s had ionic conductivity of about 1 x 10(-6) S cm(-1) at 302 K. The packing structure of PAS(Li) is discussed on the basis of powder XRD data.