The mechanical behavior of biological cells is mainly determined by the cytoskeleton. Its properties are closely interlinked with many cellular events, including disease-related processes, and, thus, may be exploited as potent biomarkers. We have stretched two types of cells between microelectrodes through the application of dielectrophoretic forces. Small numbers of cells of cancerous origin (MCF-7) and from related noncancerous tissue (MCF-10A) were sufficient to obtain data that allowed us to unambiguously distinguish these cells. The Maxwell tension applied has been estimated to be 56 Pa. A detailed analysis of the cells showed that the differences in the stretching response are due to cell-specific mechanical properties. Through the addition of an actin- and a microtubule-specific toxin to the cells, differences in the microtubular structures of the two cell types have been identified as the major cause for the behavior observed. Our approach shows enormous potential for parallelization and automation. Hence, it should be suitable for achieving throughputs that make it attractive for many biomedical diagnostic purposes.