Few studies concerned with the accumulation of trace metals by the oyster have dealt with depuration. Depuration, or a loss of metal, has been observed during gametogenesis. Spawning has also been implicated in metal loss from the oyster. Some depuration studies have been performed under controlled conditions while others have been performed under natural conditions. In most studies, some depuration of metals was observed. The effect of seawater temperature on metal depuration from the oyster remains uncertain. Shuster and Pringle (1969) reported that metal depuration proceeded more slowly at seawater temperatures of 4-12 degrees than at 20 degrees. The study of Cunningham and Tripp (1975) indicated that mercury clearance in oysters was greater when temperature was held constant at 25 plus or minus 2 degrees C than in a declining temperature regime (25 to 5 degrees C). However, Mandelli (1975) reported that winter conditions were more favorable for copper depletion in oysters. This study was an attempt to establish under laboratory conditions whether treated oysters would depurate accumulated cadmium and copper when returned to cleaner waters containing natural concentrations of these metals. In addition, an attempt was made to determine if cadmium accumulation would promote copper loss in the oyster.