K coefficient which is an integral indicator of the unbalance in the system lipid peroxidation--antioxidant system (LPO-AOS) and content of nitrite, nitric oxide end product, were followed up in 31 patients with concomitant brain injury, in 24 patients with burn injury and 72 patients in hypertensive crisis. Coefficient K was estimated by serum levels of dienic conjugates, malonic dialdehyde, lipid peroxidation degree, alpha-tocopherol, ceruloplasmin on the disease day 1, 3, 7 and 14. Nitrite serum levels rose by day 14 in all the patients and were the highest in hypertensive crisis patients. Coefficient K was significantly elevated in all the patients compared to controls being maximal in patients with concomitant brain injury. Thus, activation of LPO and biosynthesis of nitric oxide contribute much to endogenic intoxication in patients on critical care.