Indirect calorimetry was performed during the first five days after admission in 18 neurosurgical patients with isolated head - injuries (N = 7) and spontaneous intracranial hemorrhages (N = 11) to determine basal metabolic rates (BMR). In the study group each day BMR varied from 2143 +/- 636 kcal/day to 3371 +/- 1140 kcal/day. Most patients however showed BMR values between 2000 and 2500 kcal/day. Individually BMR values ranged from 60 to 340 percent of normal healthy individuals. Patients with isolated head - injuries showed significant higher metabolic rates than patients with spontaneous intracranial hemorrhages. The authors conclude that an caloric intake of 2000 to 2500 kcal/day is sufficient for parenteral nutrition and usually helps to avoid negative effects of hyperalimentation by overestimation of BMR in this special patient group.