Analyses of the concentrations of Cd, Cr, Co, Cu, Fe, Pb, Mn, Hg, Ni, and Zn in filtered waters, suspended particulates, sediments, shellfish, fish, airborne particulates, and sewage have confirmed work of other investigators showing that the Derwent Estuary is heavily contaminated, particularly with mercury, cadmium, lead, and zinc, and have added further information regarding the distribution of each metal. Apparently most of the contamination originated from the earlier operation of a zinc refining plant. A study of shellfish growing in variously contaminated regions found that more than 20 species could be listed in order of their respective abilities to accumulate each heavy metal. For example, the mussel ( Mytilus edulis) was found to be a good indicator of cadmium and mercury contamination, but less valuable as an indicator of zinc. The surf barnacle, ( Catophragmus polymerus) was found to be one of the most sensitive biological indicators of cadmium contamination. An indication of the steps by which a waste metal is eventually accumulated at high and even toxic concentrations in seafoods, may be seen from a comparison of the relative concentrations of cadmium, lead, mercury, and zinc found in mussels, sediments, suspended particulates, and filtered waters. The high concentrations recorded for metals include: 1,100 µg/g Hg, 10,000 µg/g Zn, and 862 µg/g Cd in dried sediments; 1,500 µg/g Cd in airborne dust fallout; 200 µg/g Cd and 100,000 µg/g Zn in dried oysters; and 16 µg/l Hg, 15 µg/l Cd and 1,500 µg/l Zn in filtered waters.