A series of feeding experiments was conducted to determine indispensable amino acid (IAA) requirements of gilthead seabream juveniles. The development of a balanced diet that fosters good fish growth to be used as a reference diet was the objective of the first trial. The diet selected, based on growth parameters and nutrient utilization efficiencies, resembled the whole body IAA profile of wild seabream having 55 percent of the protein component provided by crystalline amino acids. In subsequent trials the dietary lysine and methionine requirements were determined by the growth response of the fish fed on six isonitrogenous diets containing graded levels of crystalline L-lysine.HCl and L-methionine. By analysing the dose-response relationship based on weight gain percentage of the fish, to increasing levels of the test amino acid, the dietary requirements of lysine and methionine, estimated from a broken line regression, were calculated at 4.88 g/16 g N and 2.77g/16g N.