In the present investigation the changes in energy levels or caloric concentrations of Penaeus indicus postlarvae (PL) were determined after exposure to acute and sublethal concen- trations of lead. The biochemical constituents such as carbo- hydrates, proteins, and lipids were estimated in PL exposed to LC(5) (0.1495), LC(10) (0.3488), LC(25) (1.4660), and LC(50) (7.223 ppm) of lead for 48h. The effect of sublethal concentration (1.44 ppm) of lead was also studied on the above biochemical constituents at intervals of 24, 48, and 96 h, and 10 and 30 days. The caloric concentrations as well as biochemical constituents of the PL demonstrated a decrease on exposure to lead but proteins and lipids decreased to a maximum extent compared to carbohydrates. Moreover, acute concentrations were found to be more effective than sublethal lead. An increasing trend in the ratios of carbohydrate/protein and carbohydrate/lipid was observed during acute and sublethal exposure to lead, indicating more utilization of protein and lipid. Therefore, measuring the caloric concentration in PL of P. indicus can be used to evaluate the physiological effects of combating lead toxicity.