Resting energy expenditures (REE) were measured using indirect calorimetric techniques in 62 patients with burn injuries admitted during 1987 to 1989 and compared with similar measurements made during 1972 to 1973. Energy requirements were related to burn size in both populations, but were greater in the earlier population. In the present study, data from some patients were obtained using a canopy system and from others during mechanical ventilation and were analyzed separately. The regression of REE on burn size was linear for the canopy measurements (r = 0.724) and for the ventilator measurements (r = 0.579). REE data were corrected for the expected basal metabolic rate (BMR) for each patient, with appropriate adjustment for age and sex. The regression of REE per BMR on burn size was linear (r = 0.724), differing from the curvilinear relationship found during 1972 to 1973. These data suggest a change in postburn energy requirements, probably related to differences in patient management. Predictive equations based on older data can be expected to overestimate energy requirements in patients receiving modern burn therapy.