An in vitro study was performed on the uptake and subsequent binding to protein of heavy metals in isolated gill preparations of Mytilus galloprovincialis. The metals used in the study were Cd, Zn, Hg, V, Cr, Te, Tl, As and Tc. Experiments were conducted for one hour and the disappearance of metals from the water correlated with final gill-metal concentrations. Distribution of metal between 105,000 g cytosol and pellet was determined, as was the association of each metal with cytosol protein following gel-filtration chromatography. Results indicate that all metals are accumulated by the gills but that the uptake kinetics vary with each metal. Similarly, the association of each metal to protein varied for each type.