Whether to include or exclude the potential kilocalories in protein when calculating the energy provided by total parenteral nutrition (TPN) has been debated. Both methods are found in clinical practice. An attempt was made to study 52 patients for seven days, randomized to receive their total energy expenditure from TPN calculated for total calories (TC) or nonprotein calories (NPC). Many TPN patients were excluded or dropped from the study because of enteral nutrient intake, inability to perform metabolic cart measurements or nitrogen balance calculations, renal failure, or surgery during the study. Six subjects completed at least part of the protocol (three in each group). Nitrogen balance, respiratory quotient, prealbumin, blood glucose, and triglycerides were measured. Insufficient data were collected to support or dispute the superiority.