Two sets of factorial experiments were conducted for 8 weeks to determine the response of Penaeus monodon juveniles (average weights = 0.60 ± 0.16 g and 0.80 ± 0.05 g) to diets containing various protein/energy ratios. The first experiment used casein as the sole source of protein, while the other used a combination of 70%:30% casein:gelatin for its protein source. A two-fold increase in the body weight was achieved for prawns fed diet combinations of 40-50% protein, 5-10% lipid and 20% carbohydrate with energy values of 285-370 kcal/100 g, regardless of the protein source used. Reduction in protein content of the diet from 50% to 40% while maintaining the total energy level at 330 kcal/100 g resulted in a non-significant decrease in growth. The inclusion of 15% lipid in the diet produced adverse effects on the animal while sucrose levels beyond 20% resulted in a decreased growth rate. An increase in energy level, at constant dietary protein level, resulted in improved utilization of protein and feed conversion efficiency. Survival of the prawn was higher with diets containing casein and gelatin as the protein source than with those containing casein as the sole source of protein.