Polymeric conducting composites were obtained on the basis of polypropylene and polystyrene and conducting fillers (iron, copper and carbon black). The materials obtained by means of physical blends of the components were characterized through complex impedance diagrams. The respective data provided evidence of the fact that the conduction mechanism of such composites depends both on the chemical and structural properties of the polymeric matrix and on the nature of the conducting additive. © 1990 Springer-Verlag.