Growth of polypyrrole (PPy) on crystalline poly(ethylene oxide)-ferric chloride complexes has been investigated by X-ray diffraction, optical and scanning electron microscopy. PPy deposited on such crystalline substrates develops ordered structure conforming to orthorhombic configuration with lattice parameters of a=6.11, b=7.19 and c=16.31 A ̊, which has similarity to the substrate crystallites. Preferential nucleation of PPy is seen on these substrates especially when these are oriented into fibre form. No such order is observed when amorphous polymer substrates with FeCl3 are used for PPy deposition. The electrical conductivity σ depends on FeCl3 concentration c as a power law of the type σ∞c5 and has a minimum activation energy of 0.09 eV at a molar ratio of about 1:5. The various results are in keeping with the structured growth of PPy which is strongly influenced by the crystalline order in the substrate. © 1993.