The conductivity, electronic properties and morphology of polypyrrole and polyaniline films deposited from aqueous solutions of the polymerizing monomer differ greatly according to whether they are deposited on a hydrophobic or hydrophilic substrate surface. For each polymer the conductivity of the film deposited on a hydrophobic substrate is ~10 4 greater than that of the film of approximately the same thickness deposited on a hydrophilic surface. Films of increasing thickness exhibit a “memory effect” induced by the nature of the original substrate surface.