From HeLa and its multiple identities, to MDA-MB-435, erroneously and widely used as breast cancer cells, the history of cancer cell lines is rich in misidentification and cross-contamination events. Despite the fact that these problems were regularly signaled during the last decades, many actors of research still seem to ignore them. A never-ending story? Solutions exist, notably based on recent technical advances in cell line authentication (short tandem repeat analysis). However, a collaborative action involving users of cell lines, cell banks, journals and funding agencies is needed to achieve success. © 2007 Wiley-Liss, Inc.