Disease has been implicated as a contributing factor in the ongoing decline in global amphibian population sizes. In addition to disease, another factor threatening global amphibian populations is environmental contamination. A leading hypothesis to explain these declines is that environmental pollutants weaken amphibian immune function such that subsequent exposure to pathogens results in increased disease susceptibility and death. Therefore, measures of immune function provide a way to analyze how contaminant exposure may be linked to disease susceptibility. Previous research has found that polychlorinated biphenyl (PCB-126) exposure during the tadpole life stage (but not the juvenile stage alone) decreased innate and adaptive immunity in juvenile frogs following metamorphosis. However, the mechanisms underlying this life-stage specific immunotoxicity are not well understood. We will expose native tadpoles to PCB-126 and employ molecular techniques like polymerase chain reaction (PCR), enzyme-linked immunosorbent assay (ELISA), and/or RNA sequencing to identify genes and proteins that might be dysregulated in response to PCB-126. The findings of this research will help elucidate the mechanisms involved in PCB-126 toxicity in tadpoles.