The response of the plasma substrate and hormone profile of survivor and nonsurvivor septic trauma patients to varying rates of amino acid infusion (IVAA) were contrasted. When IVAA = 0 levels of most plasma amino acids (except aspartate, tryptophan, cysteine, and proline) were lower in nonsurvivors. At IVAA = 1 to 100, however, 11 of 20 plasma amino acids were significantly (p≤ 0.05) higher in nonsurvivors: only glutamate was significantly lower (p≤ 0.001) and valine, isoleucine, and arginine on average lower. At IVAA ≤ 101 to 200, only alanine, methionine, tyrosine, and phenylalanine were significantly (p≤ 0.005) higher in nonsurvivors; isoleucine was significantly (p≤ 0.02) lower. The sharp increase in methionine and decrease in tryptophan in nonsurvivors with IVAA was particularly marked.Polynomial regression analysis showed that urea increased significantly with IVAA in both patient groups, while free fatty acids and cortisol decreased only in nonsurvivors. Insulin increased with IVAA only in survivors, glucagon only in nonsurvivors. Triglycerides, glycerol, acetoacetate, β OH butyrate, and glucose appeared to show no significant response to IVAA in either patient group.The data are consistent with increased peripheral protein catabolism and branched-chain amino acid oxidation in association with decreased tissue uptake of conventional energetic fuels. These results may be interpreted to be consistent with an impairment of mitochondrial translocase systems.