Compositionally modulated layered structures are fabricated in polypyrrole-poly (3-methylthiophene) composite thin films by the potential-programmed electropolymerization method reported previously (T. Iyoda, H. Toyoda, M. Fujitsuka, R. Nakahara, H. Tsuchiya, K. Honda and T. Shimidzu, J. Phys. Chem., 95 (1991) 5215). The depth profilings by secondary ion mass spectrometry, Auger electron spectroscopy, transmission electron microscopy and electron probe microanalysis indicate that the resulting thin films have compositionally modulated layered structures, consistent with the designed structures. The diversified profiling by the above techniques is an extremely valuable means of analysing the layered structures of these conducting polymer thin films in terms of their periodicity and compositional modulation.