Poly(aniline)-nylon 6 composite film (PANI-N) prepared by diffusion and chemical oxidative polymerization has very low percolation threshold contents (similar to 4 wt%) and provides a high conductivity. Hydrogen bonding between poly(aniline) (PANI) and nylon 6 is found to affect the doping characteristics of PANI-N. From the results of dynamic mechanical thermal analysis, the crystalline regions of nylon 6 in the composites are found to be affected by the formation of PANI. From u.v.-visible spectra, it is considered that the thermal cross-linking reaction of PANI may be reversibly changed by the chemical doping and de-doping processes. (C) 1997 Elsevier Science Ltd.