Adults of the bay scallopArgopecten irradians were held in flowing seawater containing 5 or 10Μg Cu/kg at ambient temperature and salinity. After eight weeks, scallops contained up to 91 and 310Μg Cu/g dry weight, respectively, in the total soft parts. Copper uptake was linear over time. There was no significant relationship between dry weight and copper content (Μg) in adductor muscle, visceral mass or total soft tissue. However, there was a significant inverse relation between dry weight and copper concentration (Μg/g) in adductor muscle, visceral mass, and total soft tissue. A decrease in copper content occurred in the visceral mass and total soft parts during spawning in the control and 5 Μg Cu/kg treatments. There was no apparent decrease in copper concentration during spawning in any tissue of scallops from all three treatments.Argopecten irradians is an excellent bio-indicator of copper, since accumulation was observed in the visceral mass at a seawater copper concentration of 1.8Μg/kg.