Cell culture and the use of cell lines are routinely used in basic scientific research. It is therefore imperative for researchers to ensure the origin of the cell lines used and that they are routinely re-analysed for contamination and misidentification. Inter-species contamination is relatively frequent, and the most commonly used cell lines are of human, mouse and rat derivation. We have developed simple species specific primer assays based on genomic sequence differences in vomeronasal receptor gene family members to discriminate between human, mouse and rat DNA using standard agarose gel electrophoresis. Furthermore, these PCR assays are able to identify the species composition within an inter-species mixed population. This approach therefore provides a valuable tool to enable a rapid, simple and relatively inexpensive determination of the authentication and contamination of cell cultures.