Carbon black filled conductive rubber composites have been derived from EVA, EPDM and their blends. The electrical and mechanical properties of the composites have been investigated. The critical concentrations for achieving high conductivity have been explained on the basis of the polarity of the base rubber. The temperature dependence of volume resistivity of the composites shows a negative temperature coefficient (NCT). The activation energy of conduction decreases with increase in the loading of conductive filler. The shape of the hysteresis loop observed during the heating and cooling cycle i.e., the variation of volume resistivity with temperature depends on the filler concentration, which is mainly due to some kind of irreversible change occurring in the conductive networks.