Combined effects of temperature and a toxic metal, cadmium (Cd), on energy metabolism were studied in a model marine bivalve, the easternoyster Crassostrea virginica, acclimated at 20, 24 and 28 ◦C and exposed to 50 g l−1 of Cd. Both increasing temperature and Cd exposureled to a rise in standard metabolic rates, and combined stressors appeared to override the capability for aerobic energy production resultingin impaired stress tolerance. Oysters exposed to elevated temperature but not Cd showed no significant change in condition, survival rate andlipid peroxidation, whereas those exposed to both Cd and temperature stress suffered high mortality accompanied by low condition index andelevated lipid peroxidation. Furthermore, RNA/DNA ratios indicative of protein synthesis rate, and levels of glutathione, which is involved inmetal detoxification, increased in Cd-exposed oysters at 20 ◦C but not at 28 ◦C. Implications of the synergism between elevated temperatures andcadmium stress on energy metabolism of oysters are discussed in the light of the potential effects of climate change on oyster populations inpolluted areas.