In the past several years, the macroscopic electric and elastic properties of conductive polymeric composites have been studied from the viewpoint of such applications as thermistors and pressure sensors. In particular, we studied carbon black ŽCB. polymeric nanocomposites on macro- and nanoscales, using polyisoprene as the composite matrix. The filler component was an extra conductive carbon blackŽPRINTEX XE2, DEGUSSA.with a primary particle diameter of about 30 nm. A very strong reversible tensoresistive effect of electric resistance dependence on uniaxial tension deformation was observed in composites with the 10 carbon black mass parts added to 100 mass parts of polyisoprene. A conductive-type atomic force microscopeŽAFM.was used for the mapping of carbon black conductive network into an insulating matrix, while for studying the nanomechanical properties of composites, a tapping mode atomic force microscope was applied. A correlation between macroscopic and nanoscopic—both electric and elastic—properties was observed.