A high piezoresistive effect ( Δp po = 102 kg-1cm-2) has been observed in semiconducting polyvinylidene fluoride as well as polyphenylene sulfide composites containing metallic fillers. The nonlinear current-voltage characteristics conforming to the space charge limited conduction mechanism present at the interparticulate region can give rise to the observed high sensitivity of resistance to external pressure. The results predicted by this model have been confirmed by the experimental findings. © 1994.