The dietary copper requirement of Penaeus vannamei juveniles was investigated using casein/ gelatin based semi-purified diets under controlled laboratory conditions. Twenty-day-old P. vannamei postlarvae were fed the basal diet lacking copper supplementation but containing 2.0mg Cu/kg for a 10-day period to reduce tissue stores of copper. After conditioning, six replicate groups of juvenile shrimp (mean weight 0.057g) were fed each diet containing graded levels of supplemental copper (0, 4, 8, 16, 32, 64, or 128mg Cu/kg diet) for the duration of a 42-day feeding trial. Weight gain (percent weight gain) ranged from 2.88g (5, 064%) for shrimp fed the basal diet without supplemental copper (2mg total Cu/kg diet) to 3.5g (6, 177%) for shrimp fed the basal diet supplemented with 64mg Cu/kg. Weight gain of shrimp increased in response to copper supplementation up to 32mg Cu/kg diet, indicating a dietary copper requirement of no more than 34mg total Cu/kg diet. In addition to depressed growth, shrimp fed copper-deficient diets had enlarged hearts and depressed copper levels in the hemolymph, carapace, and hepatopancreas. There was no clear indication that supplementation of up to 128mg Cu/kg diet adversely affected shrimp growth or survival.