Understanding interactions between trace elements is vital to determining the potential effects of industrial waste on aquatic ecosystems. Interactions between mercury (Hg) and selenium (Se) are well known in aquatic organisms, with reduced Hg bioaccumulation and toxicity observed in the presence of Se. However, understanding of the underlying mechanism of these interactions is still lacking. As Se may play a role in redistributing Hg to less sensitive organs, it is essential to investigate these interactions in metamorphosing amphibians. Amphibians may be more susceptible to changes in toxicity due to the complex nature of metamorphosis; with the remodelling and degeneration of tissues there is the potential for the redistribution of contaminants among organs. As such, we investigated the biokinetics and interaction of Hg and Se and determined changes in biodistribution during metamorphosis of Limnodynastes peronii tadpoles. Tadpoles were exposed to inorganic 203Hg (as HgCl2) ,75Se (as Na2SeO3) or a combined 203Hg and 75Se treatment through diet or aqueous exposure. Biokinetics were determined using live-animal gamma spectrometry and changes in biodistribution were determined through gamma spectrometry and photo-stimulated luminescence autoradiography. Results from dietary exposure indicate there was no difference in Hg retention between treatments, whereas tadpoles exposed to Se alone had a greater retention rate of Se than those in the combined treatment. Biodistribution was also similar across treatments, with most of the Hg and Se in the liver, gut and muscle tissue. More research is needed to understand how the movement and concentration of contaminants during metamorphosis may affect toxic responses in amphibians. As well as this, the interactions of metals through different exposure methods must be considered in determining realistic exposure responses.