Oysters (Crassostrea virginica) showed positive growth response when fed artificial diets of known nutrient composition; differences in growth rate, meat weights, and glycogen content corresponded with differences in dietary composition. High levels of dietary carbohydrate resulted in greater oyster glycogen production. The type and level of lipid in the diet was also important. Cod liver oil was of higher nutritional value for the oysters than corn oil; increasing the dietary lipid from 5 to 18% of the dry weight, resulted in greater meat production and earlier total weight gains considered to be associated with earlier gonadal ripening.Oysters held in Malpeque Bay in floating trays grew 10 times faster than those held in tanks of continuously flowing filtered sea water and fed artificial diets.