An increase in scholarly publishing has been accompanied by a proliferation of potentially illegitimate publishers (PIPs), commonly known as "predatory publishers." These PIPs often engage in fraudulent practices and publish articles that are not subject to the same scrutiny as those published in journals from legitimate publishers (LPs). This places academics at risk, in particular students who utilize journal articles for learning and assignments. This analysis sought to characterize PIPs in physiology, as this has yet to be determined, and identify overlaps in lists of PIPs and LPs used to provide guidance on legitimacy of journals. Searching seven databases (2 of PIPs and 5 of LPs), this analysis identified 67 potentially illegitimate journals (PIJs) that explicitly include "physiology" in their titles, with 8,801 articles being published in them. Of these articles, 39% claimed to be indexed in Google Scholar, and 9% were available on PubMed. This resulted in 17 publications "infiltrating" PubMed and attracting >100 citations in the process. Overlap between lists of PIPs and LPs was present, with eight PIJs occurring in both LP and PIP lists. Two of these journals appeared to be "phishing" journals, and six were genuine infiltrations into established databases, indicating that LP lists cannot be solely relied on as proof a journal is legitimate. This analysis indicates that physiology is not immune to the threat of PIPs and that future work is required by educators to ensure students do not fall prey to their use.