Introduction: Advances in scientific research are based on previously published findings. However,there is concern about the lack of reproducibility in the biological researches in basic and preclinical areas, due to the repercussion on the population´s health. Because in vitro cultured cells are the basis for many toxicological and therapeutic studies, concern about their quality becomes paramount. Regarding microbiological contaminants, although bacteria and fungi are easily recognized, viruses and mycoplasmas are invisible under light microscopy. Another delicate issue would be the results generated with cells with modified identity. Objective: To discuss the main methodologies for assuring the quality of cells used in in vitro assays and to demonstrate how some world collections are structured to address this issue. Method: The scientific literature in the PubMed and Scielo databases and the webpage of different biological collections until December 2017. Results: It is recommended to apply the following techniques to detect contaminants in cell cultures: 1) virus : PCR and viral isolation; 2) mycoplasmas: PCR,bioluminescence and staining of cells with DNA affinity fluorophore; 3) human cell identity: the STR; 4) non-human cell identity: the Barcode. Conclusions: Considering all the investment applied in scientific research worldwide, the development of new methodologies alternatives to the use of animals and the critical consensus of the concept of quality, it is concluded that any laboratory should guarantee the control of purity and authenticity of its lineages.