The relationship between cadmium exposure dose and response was investigated in Anadara trapezia exposed to cadmium spiked sediment (10 Î¼g/g and 50 Î¼g/g dry mass) for 56 days. A. trapezia reached an equilibrium cadmium tissue concentration (13 Î¼g/g and 25 Î¼g/g, respectively) by day 42. Gills accumulated significantly more cadmium than the hepatopancreas and haemolymph. After 56 days exposure between 46 and 73% of accumulated gill and hepatopancreas cadmium was detoxified and in the metallothionein like protein fraction. Approximately half of the biologically active cadmium in both tissues was in the mitochondrial fraction which has the potential to cause dysfunction in mitochondrial activity. Cadmium exposed A. trapezia generally had reduced GPx activity with an associated increase in total glutathione concentrations and reduced GSH:GSSG ratios due to a build up of oxidised glutathione. The changes in the glutathione pathway were reflected in the total antioxidant capacity of cadmium exposed A. trapezia which were significantly reduced compared to control organisms. There was a trend of increased lipid peroxidation with increased cadmium exposure but this was not significant. Increased cadmium exposure resulted in significant lysosomal destabilisation and increased frequency of micronuclei. The significant exposure-dose-response relationship for A. trapezia exposed to cadmium enriched sediments indicates that elevated sediment cadmium concentrations have the potential to lead to increased biologically active cadmium burdens and impairment of individual A. trapezia at cellular and subcellular levels.