It is known that a green oyster was resulted from normal one to absorb and to accumulate heavy metals. The cultured oysters in Miyako Bay of Iwate Prefecture were greened in November, 1969. Copper contents in the fresh bodies of green oysters in Miyako Bay were estimated as 48 to 65ppm and zinc contents were 324 to 511ppm. On the other hand, copper contents of normal oysters in Yamada and Ofunato Bays were ranged from 14 to 20ppm and zinc from 156 to 164ppm. Of the contents of the heavy metals in cultured oysters hanging in the sea water, their highest values were found in the oysters near sea surface, and their lower values in those at the deeper places. It was observed that the accumulated copper and zinc were found at higher levels in the green meat than in the white meat of the oyster.