Transparent and conducting coatings of a polyaniline(PANI)/polymethyl methacrylate(PMMA) or PANI/polyvinyl chloride (PVC) composites were prepared by chemical polymerization in situ onto the surface of transparent sheets. Their surface resistances and transparencies were measured as functions of the concentrations of aniline monomer and oxidizer, oxidation time, thickness of the coatings and the matrix polymers used, etc. A typical coating layer with surface resistance of 10(3)-10(4) Omega/square and transparency of 60%-70% at 500 nm on the surface of a transparent sheet can be obtained. Some differences in the surface resistance and transparency values between PANI/PMMA and PANI/PVC coatings were observed, which may be caused by differences in their morphologies. The conduction mechanism of these coatings can be described by a charge-energy-limited tunnelling model.