The Biofidelity Ranking System has been implemented in a variety of studies since its inception in 2002 to assess the biofidelity of anthropomorphic test device and model responses against a human response. Four chronological versions have been developed with each new version altering how biofidelity scores are calculated. However, it is unknown if and how differences in Biofidelity Ranking System versions affect the resulting biofidelity scores and the conclusions of the studies that implement them. Therefore, the objective of this study was to compare the biofidelity scores of the 2009 and 2018 versions of the Biofidelity Ranking System by applying both versions to the same dataset. The dataset in this study consisted of matched Hybrid III and THOR 50th percentile male sled tests and included 101 response signals from each anthropomorphic test device. The results of the analysis indicated that the 2018 version produced significantly lower (better) scores for individual response measurements than the 2009 version and a significantly better overall biofidelity assessment, depending on how the individual response scores were averaged. This finding implies that using different versions of the Biofidelity Ranking System on the same dataset may affect the biofidelity results and conclusions. Based on the results of this study, recommendations for transparently using the Biofidelity Ranking System are provided.