During the 1950s, cross-contamination of cell lines emerged as a problem with serious consequences on the quality of biomedical research. Unfortunately, this situation has worsened over years. In this context, some actions should be urgently undertaken to avoid the generation of misleading data due to the increasingly and sometimes neglected use of cross-contaminated cell lines. Unawareness about this problem may then turn many scientists into victims or even perpetrators of this unwanted situation. Collaborative actions involving researchers, cell banks, journals, and funding agencies are needed to save the scientific reputation as well as many public or private resources that are used to produce misleading data.