The early larval development of Siganus guttatus was studied with emphasis on the transition From endogenous to exogenous feeding. Three rearing trials were conducted as follows: 1) rear-ing in a 5 ton concrete tank at 27.9-29.3°C (T-85 trial); 2) rearing in a 0.5 ton fiberglass tank at 22.2-26.5°C(T-86A trial); 3) rearing in the same manner as in T-86A but without food (T-86B trial). On the basis of the developmental events and energy flow in T-86A trial, the early life history of the species could be divided into the following seven phases: 1) rapid larval growth due to rapid yolk resorption (from hatching to about 15h after hatching (time after hatching: TAH)); 2) slow growth and organogenesis based mainly on yolk energy (to about 50h TAH); 3) slow growth based on energy of yolk, oil globule and exogenous food (to about 70h TAH); 4) slow growth based on two sources of energy, oil globule and exogenous food (to about 90h TAH); 5) the same mode of development and energy flow as in the preceding phase, but with a certain level of feeding amount (to about 120h TAH); 6) accelerated larval growth and effective feeding and swimming based only on exogenous food (to about 150h TAH); and 7) the same mode as in the preceding phase with accelerated increase of feeding amount (beyond 150h TAH). Differences in developmental mode were observed in T-85 and T-86A trials, but it could not be ascertained in this particular study which of the environmental factors played the greatest influence. The results of T-86A and B showed that the larvae, in order to survive, have to get over two obstacles on feeding, that is, to start feeding and to change from endogenous to exogenous feeding suitably.