Aim. To study features of endogenous intoxication syndrome (EI), oxidative stress (LPO) and antioxidant defence (AOS) in patients with acute lower limb ischemia (LLI).Materials and methods. Some parameters of EI, LPO and AOS were studied. EI syndrome was studied in 86 patients with LLI who underwent complex examination and treatment in 2020-2021 in the Department of Vascular Surgery of the RNCfCS. POL and AOS parameters were studied in 14 patients out of 86. There were 51 (59.3%) men and 35 (40.7%) women, mean age was 56.0±5.8 years. Acute occlusion of the iliofemoral segments was noted in 33 (38.4%) patients, in 32 (37.2%) - the femoral segment, and in 21 (24.4%) - the popliteal and femoral vessels. In all cases, ischemia had a unilateral localization - on the right in 59 (68.6%) cases and on the left in 27 (31.4%) cases. In 52 (58.1%) cases, there were clinical signs of grade II b ischemia, and in 36 (41.9%) cases - grade III A (according to V.S. Saveliev, 1987). The average duration of ischemia was 77.9±28.3 hours.Results and discussion. In all cases of LLI before revascularization, there were signs of acute inflammatory reaction and EI syndrome in the form of increased ESR (42.3±7.1 mm/h), CRP concentration (16.1±4.2 mg/L), fibrinogen (8.5±0.9 g/L) and leukocytosis (12.7±1.5×109/L). Also, all patients had a slight elevation of blood glucose against the background of EI (7.5±1.8 mmol/L), a significant increase of creatinine concentration (128.9±6.1 µmol/L), urea (9.2±0.6 mmol/L) and aminotransferases as compared to normal indices. Results of LPO and AOS indices study in 14 patients showed that in LLI, malondialdehyde (MDA) increases 2.6-fold (3.9±0.1 μmol/L), diene conjugate increases 3.7-fold (0.77±0.04 units a/mL). However, after the elimination of ischemia, there was no significant decrease for 12.2±2.4 days, which confirms the presence of reperfusion syndrome. AOS indices - superoxide dismutase (20,8±1,0 u/l) and catalase (128,9±11,2 μl/l) increased 1,2 and 1,1 times in the examined patients cohort, respectively. Statistically significant associations were established between the following indices: Ischemia level and urea (r=0.89), Ischemia level and white blood cell count (r=-0.82), Hb and Er (r=0.99), Hb and creatinine (r=0.79), Hb and urea (r=0.79), Er and urea (r=0.79), creatinine and Er (r=0.90), ACTV and creatinine (r=-0.77), creatinine and urea (r=0.90).Conclusion. Acute lower limb ischemia is accompanied by ischemia-reperfusion damage manifested by endogenous intoxication syndrome, impaired glucose metabolism and activation of lipoperoxidation processes and antioxidant system. After the elimination of acute ischemia, there is not always a significant decrease in lipid peroxidation and some inflammation parameters. Therefore, prolonged use of antioxidants in the reperfusion period is recommended.