The prawn Penaeus japonicus was reared with diets containing3%soybean lecithin(diet A)and no supplemental phospholipids (PL) (diet D)for 30 days. The deficiency of PL in dietssignificantly reduced the weight gain and feed conversion efficiency. The prawns receiving diet D without supplemental PL contained a lower concentration of PL such as phosphatidylcholine and phosphatidylinositol in the whole body than the ones receiving diet A with supplemental PL. The retention (%) of dietary lipids, especially cholesterol, in the body was also significantly lowerin the prawns receiving diet D than in those receiving diet A. These data indicate that the juvenile prawn requires dietary sources of PL for good growth; suggesting that the dietary PL may benecessary for the effective utilization of lipids such as triglycerides and cholesterol in the diets bythe prawn.