The correlation between energy expenditure and hormonal changes following surgical stress was studied using rats. Blood concentrations of catecholamine, insulin, corticosterone, glucagon, T3, and T4 were compared between the rats (IIa and IIb) in the ebb phase and those (III and IV) in the flow phase, 6 hours after being inflicted with a burn. Noradrenaline was higher, though not significantly, and glucagon was significantly higher in the latter groups than in the former groups. When glucagon was administered to the rats in the ebb phase, RME increased significantly. From these results, it is suggested that glucagon plays an important role in the transition from ebb phase to flow phase.