Camphor sulfonic acid (CSA)-doped poly(o-anisidine) (PoAN) has been found to possess the electrical conductivity of 10 S/cm. This value is rather low compared to that of (approximate to 200 S/cm) CSA-doped polyaniline, which may arise from a limited transformation of coil-like conformation to an expanded one. Viscosity data and optical absorption spectra provided strong evidence for the existence of coil-like CSA-doped PoAN chains in m-cresol. The shift of IR bands of benzenoid and quinoid rings toward a lower wave number and the appearance of the bands at approximate to 1600 and 1173 cm(-1) (the IR is inactive but becomes active on doping) suggested the protonation of CSA-doped PoAN. The thermogravimetric profile of CSA-doped PoAN showed a five-step decomposition pattern with the thermal stability up to 134 degrees C. The mass spectra taken simultaneously with the thermogram revealed that dopant CSA is completely eliminated around 360 degrees C, but the breakdown of polymer chains does not occur very briskly at this temperature. Composites of CSA-doped PoAN with insulating acrylonitrile-butadiene-styrene copolymer (ABS) were fabricated, and it was found that the composites showed a percolation behavior in which the electrical conductivity rose sharply at about 4 weight % of CSA-doped PoAN in the ABS composite. The STM data demonstrated the formation of a continuous path at the percolation threshold. The Poole-Frenkel effect was observed for the conduction scheme in the CSA-doped PoAN/ABS composite.