The mercury and selenium contents of fresh seafood were determined, respectively, by means of cold vapor atomic absorption spectroscopy (CVAAS) and hydride-generation atomic absorption spectrometry (HGAAS). All the values obtained were lower than the European Union´s legal limit of 0.5 mg/kg fresh food, rising to 1.0 mg kg for the edible parts of some listed species; in fish they vary between 0.057 mg/kg in sole and 0.579 mg/kg in swordfish (included in the category of large fish, for which the legal limit is 1 mg/kg). The levels of selenium vary between 0.073 mg/kg in perch and 0.743 mg/kg in tuna. In shellfish the mercury content varies between 0.023 mg/kg in moscardino and 0.150 mg/kg in Mediterranean shrimp, while that of selenium varies between 0.067 mg/kg in spiny lobster and 0.605 mg/kg in mussels. A significant difference was found between fish and shellfish for mercury, but not for selenium. A large excess of selenium in relation to mercury was observed (the mean molar ratio of Hg/Se is 0.23 for fish and 0.09 for shellfish), but no significant correlation was found between the two elements.