This study examines the relationship of burn injury and plasma levels of conjugated dienes, total sulfhydryl groups, and vitamin E in patients with thermal injuries. Plasma neopterin levels were determined as an index of macrophage activity and serine elastasc as an index of polymorphonuclear cell activation. Thirteen patients with burns, six survivors and seven nonsurvivors, were studied for the first 4 days, then every other day until postburn day 14. Twelve healthy volunters served as the control group. Survivors had 56% ± 4% total body surface area burned, and nonsurvivors had 63.9% ± % total body surface area burned. The patients with burns, compared with the control group, showed elevated plasma levels of the lipid peroxidation products conjugated dienes (0.767 ± 0.045 vs 0.269 ± 0.013 Abs at 233 nm) and reduced levels of the natural scavengers of free radicals, vitamin E (196.2 ± 12.6 vs 841.1 ± 22.7 ng/dl) and total sulfhydryl groups (54.0 ± 0.4 vs 15.8 ± 1.0 (j.mol/dl). The total sulfhydryl groups/conjugated dienes ratio fell at a greater rate (9.8% ± 3.2% vs 3.2% ± 0.7%/day) in nonsurvivors than in survivors (p<0.05 by Mann-Whitney). The levels of elastase were slightly elevated in the patients with burns, but there was no difference between survivors and nonsurvivors. Normal neopterin levels are 3 to 10 nm/L; peak levels were 119 ± 48 nm/L in nonsurvivors and 37.4 ± 10 nm/L in survivors. Patients widi burns demonstrated evidence of increased oxygen free radical activity and activation of polymorphonuclear cell and macrophages. Nonsurvivors demonstrated increased consumption of antioxidants compared with survivors. The difference between the levels of oxidation appear to be related to activation of macrophages. Considering the importance of vitamin E as an antioxidant and its deficiency in patients widi thermal injuries, supplementation of the diet of patients with burns widi a tocopherol is warranted.