Current European regulations define in vitro expanded cells for clinical purposes as substantially manipulated and include them in the class of Advanced Therapy Medicinal Products to be manufactured in compliance with current Good Manufacturing Practice. These quality requirements are generally thought to be elaborate and costly. However, they ensure three main product characteristics: safety, consistency, and absence of cross-contamination. The term crosscontamination is used to indicate misidentification of one cell line or culture by another. The Good Manufacturing Practice Guidelines suggest some recommendations in order to prevent cross-contaminations and require a demonstration that the implemented actions are effective. Here we report some practical examples useful both to minimize crosscontamination risks in an Advanced Therapy Medicinal Products production process and to evaluate the efficacy of the adopted measures.