The seasonal dynamics of Mn, Fe, Zn, Cu and Cd were investigated in a genetically similar population of hatchery-reared American oysters, Crassostrea virginica, maintained in plastic trays in the Rhode River, a tributary of the Chesapeake Bay. Samples were collected monthly from September, 1971 through May, 1973. Annual cycles resulting in the turnover of large portions of the body burden were observed for all metals studied. Subtly different patterns of metal dynamics were observed as a result of the reduction in biological variations realized by employing genetically similar oysters. Metals are grouped into two classes according to their dynamics: (1) Mn and Fe concentrations in soft tissues are significantly correlated with shell deposition. A high rate of Mn turnover in soft tissues (approximately 2 times the body burden per day) occurs during the shell growth season. (2) Zn and Cu concentrations are not correlated with shell growth. Zn and Cu body burdens exhibit a gradual increase during the spring and early summer followed by a rapid loss during August–September in which 33% of the Zn and 50% of the Cu is lost in less than 4 weeks. Cd behavior is similar to zn and Cu with a 50% reduction in body burden during an 11 week period between July and October.