The variation of electrical resistivity of carbon black and short carbon ®bre (SCF) ®lled rubber composites was studied against the degree of strain at constant strain rate. It was found that both the degree of strain and strain rate affect the electrical resistivity of the composites. The change in resistivity against the strain and strain rate depends both on the concentration and the type of conductive ®ller. The incorporation of short carbon ®bres (SCF) imparts higher conductivity to the composite than carbon black at the same level of loading. Composites ®lled with carbon black exhibit better mechanical properties than SCF ®lled composites. Electrical setting, ie a permanent change in electrical resistivity, was observed during extension±retraction cycles. A good correlation was found between the mechanical response and the electrical response towards strain sensitivity. The results of different experiments are discussed in the light of breakdown and formation of conductive networks in the ®lled rubber composites.