Scanning force microscopy was used for the determination of the elastic properties of living cells in their culture conditions. The studies were carried out on human epithelial cells. Two similar lines of normal cells (Hu609 and HCV29) and three cancerous ones (Hu456, T24, BC3726) were measured using the scanning force microscope in order to collect the force versus indentation curves. The BC3726 line originates from the HCV29 cell line which was transformed by the v-ras oncogene. To evaluate their elastic properties, Young's modulus values were determined. The present study has shown that normal cells have a Young's modulus of about one order of magnitude higher than cancerous ones. Such a change might be attributed to a difference in the organisation of cell cytoskeletons and requires further studies.