We measured energy expenditure (MREE) and nitrogen excretion (UUN) in patients with severe head injury randomized to early parenteral (TPN, n = 21) or jejunal (ENT, n = 27) feeding with identical formulations. The MREE rose to 2400 +/- 531 kcal/day in both groups and remained at 135% +/- 26% to 146% +/- 42% of predicted energy expenditure over 4 weeks. Nitrogen excretion peaked the second week at 33.4 +/- 10 (TPN) and 31.2 +/- 7.5 (ENT) g N/day. Both routes were equally effective at meeting nutritional goals (1.2 x MREE, 2.5 g protein/kg/day intake, stabilized albumin and transferrin levels). Infections were equally frequent: 1.86 episodes/TPN patient versus 1.89 episodes/ENT patient. While patient charges were much greater for TPN, the hospital costs were similar for TPN and ENT support regimens. These findings show that patients with head injuries are hypermetabolic for weeks, that only 27% are capable of spontaneously eating nutritional requirements by discharge, and that either TPN or ENT support is equally effective when prescribed according to individual measurements of MREE and nitrogen excretion.