Most unfilled elastomers exhibit a high electrical resistance. Fillers are usually added to elastomers to enhance their mechanical properties. Frequently the filler type used is an electrically conductive carbon black and the inclusion of such fillers reduces the resistivity of the elastomer compound. Previous work has shown that for elastomers containing high abrasion furnace, carbon black fillers such as N330 (or N300 series) at a volume fraction above the percolation threshold the resistivity changes with strain, the precise resistivity versus strain behavior being nonlinear and irreversible for conventional carbon black fillers. A strain-measuring device, deriving strain directly from a measure of the resistivity, requires that the behavior be reversible and reproducible from cycle to cycle. This work presents the electrical resistivity behavior of a natural rubber (NR) compound filled with Printex XE2 carbon black. This type of filler has a significantly different morphology to the N300 series blacks examined previously. The Printex was incorporated into the rubber at a volume fraction above its percolation threshold and its behavior is contrasted to that observed with N300 series carbon black-filled NR. Here, and for the first time, reversible electrical resistivity dependence with strain is reported for an elastomer filled with Printex XE2. This reversible behavior under strain opens up the Possibility Of applications, Such as a flexible load sensor, pressure sensor, or switch. (C) 2009 Wiley, Periodicals, Inc. J Appl Polym Sci 116: 541-546, 2010