This work has shown the sensitivity and uniqueness of conductivity and dielectric constant transient response to compressional stress for natural rubber filled with specific types of carbon black. The strong correlation between conductivity and capacitance (both steady-state magnitudes and transients) is attributed to the polymer itself. A qualitative model for these effects is based on changes of conductive and resistive microelements due to fracture of the carbon black matrix. Transient electrical measurements of this type should be applicable to carbon-black- (or metal-) filled dielectrics over a large range of resistivity.