The metabolic effects of different time schedules in postburn intragastric feeding were studied in 32 severely burned guinea pigs, divided into four groups. All groups received continuous pump-controlled feeding with a high-protein diet for 14 days postburn. Groups 1 and 2, semistarved for 72 and 24 hours, respectively, before receiving intragastric feeding (at 175 kcal/kg/day and 155 kcal/kg/day, respectively), showed a hypermetabolic response significantly greater than group 3, which started feeding at 175 kcal/kg/day immediately postburn (P<0.005). After 14 days, groups 1 and 2 had significantly greater weight loss (P<0.001), depletion of muscle mass (P<0.005), and carcass weight (P<0.01). In group 3 these nutritional values were not significantly altered. Group 4, fed at a higher caloric intake (200 kcal/kg/day) after 72 hours' semistarvation, also showed hypermetabolism and catabolism. These results indicate that immediate intragastric feeding prevents hypermetabolism and marked catabolism after severe burns.