The Paper Mate pen does carry on its package a warning to purchasers regarding the use of the pen on valuable documents. However, Swiss researchers decided to test the pen on six kinds of paper, erase the ink with four different kinds of erasers, and to attempt to cover up the ink from the pens with typical forgers' chemical treatments. In addition, several tests were run to discover whether the pen left impressions in the paper even though the ink was erased. The tests showed that the pen's mark could be erased several hours after the ink's application, but not on all the papers and that the ink did resist erasing after a certain number of hours, except for several papers which allowed erasing beyond 48 hours. Other ballpoint pens used in a control test erased badly very soon after use). On some papers the impressions left by the pen were easily detectable with classical laboratory equipment (microscopes, chemical tests), while on others it was impossible to establish that an erasure had taken place. Therefore, it is risky to use the pen on important papers. Yet, while due caution must be taken by purchasers of such pens, banks, attorneys, and businesses should be aware of the kinds of papers that take ink well and allow erasures to be detected. Persons responsible for important papers should ensure that the proper inks and the proper kind of papers are used, and that their clients are well aware of the risks involved in using Eraser Mates. The kinds of erasers and paper, and the chemical tests used to discover impressions are mentioned. --in French.