The dielectric behaviour of a composite system of epoxy resin filled with Kevlar fibres and Aluminum powder is investigated in the frequency range 20 Hz to 10 MHz and the temperature interval 10 to 150 degrees C. Dielectric permittivity is increasing with filler content and temperature, being always higher in the low than in the high frequency range. Dielectric permittivity and loss of the composites is mostly affected by interfacial polarization arising from inhomogeneites at interfaces introduced by the fillers. Equations based on the extension of the logarithmic law of mixtures are formulated and their applicability tested with the experimental data obtained.