Persistent Organic Pollutants (POPs) are still used for agricultural and disease vector control, as well as for industrial purposes. In the last decades, various studies have shown that fish are sensitive to the toxicological effects of certain POPs, including a large class of endocrine- disrupting chemicals (EDCs). In the present study, the relationship between of POPs and their effects using vitellogenin gene expression as biomarker of effect in hardhead catfish Ariopsis felis (Linnaeus, 1766) from three ecosystems in the Southern Gulf of Mexico and Yucatan Peninsula are discussed. Contaminant results showed that median concentrations of PCBs, HCHs, DDTs and Chlordanes were higher in Laguna de Terminos with respect to Celestun and Dzilam. In the same way, the vitellogenin gene expression was clearly over-expressed in fish collected from Terminos Lagoon. Principal Component Analysis showed that vitellogenin gene expression is related to the concentrations of total DDTs and PCBs, and negatively related to total Drins. Overall, this study represents the first tests exploring changes in molecular diagnostic indicators following exposure of several organic compounds in our country. Vitellogenin gene expressions associated with some endocrine disruptors detected in Terminos Lagoon were measured and we can now report clear changes in fish exposed.