1. Gonad growth and oocyte cytoplasmic growth were induced in scallops exposed to 15°C with food. At 5° C only oogonia developed.2. Scallops injected with 14C-leucine and measured 24 hours after injection showed greater incorporation of labelled amino acid into both digestive gland and gonad at 15° C than at 5° C, but the difference in uptake between the two groups was not significant.3. Incorporation of 14C-leucine into gonads of scallops measured one week after injection was significantly higher at 15° C than at 5° C.4. The gonad growth and oocyte growth of scallops is controlled by food and temperature. Both external environmental factors and the stage of oocyte development seem to regulate nutrient transfer to gonads and therefore control growth activity.