Specimens of Riftia pachyptila and Alvinella pompejana were collected during the Biocyarise expedition to hydrothermal vents on the East Pacific Rise at 13 degree N. Quantitative data describing the concentrations of metals in Riftia pachyptila showed that numerous metals are highly concentrated. Analyses of tissues reveal that the plume and the trophosome are the main sites of metal accumulation. Bioconcentration links with the mineral composition of the vent environment are discussed. Mechanisms for metal detoxication were investigated in both species: the presence of metal-rich granules and metallothionein-like proteins were observed. The role of chemolithotrophic bacteria in these mechanisms is discussed.