OBJECTIVE The purpose of the study was to determine the level of substances damaging the vascular endothelium, as well as to assess their effect on the functional state of the endothelium and the course of obliterating atherosclerosis of lower limb arteries. METHODS The study included a total of 112 people, subdivided into three groups: those with an unfavourable course of obliterating atherosclerosis of lower limbs arteries (n=48) - group 1, patients with obliterating atherosclerosis of lower limbs arteries with a conventionally favourable course (n=48) - group 2, and apparently healthy volunteers (n=16). In all subjects, the following parameters were analysed: stable metabolites of nitric oxide II, endothelin-1, homocysteine and basal insulin. RESULTS The level of stable nitric oxide metabolites (p<0.001 as compared with group 1; p<0.045 compared with group 2) was lower in the groups of patients with obliterating atherosclerosis of lower limb arteries (88.5±7.3 μmol/L in group 1; 161.5±8.6 μmol/L in group 2) as compared with healthy volunteers (226.0±28.6 μmol/L). In its turn, the level of nitric oxide was statistically significantly lower (p<0.001) in group 1 patients as compared with those of group 2. The level of endothelin-1 turned out to be higher (p<0.001) in group 1 (2.1±0.1 ng/ml) as compared with group 2 (1.6±0.1 ng/ml). Comparing group 1 patients with healthy volunteers (1.4±0.1 ng/ml), the level of endothelin-1 had also higher values (p<0.001). The level of endothelin-1 did not differ (p=0.270) as compared with group 2 and healthy volunteers. Comparing the homocysteine level in patients of the examined groups (20.7±0.8 μmol/L in group 1 patients and 18.1±0.6 μmol/L in group 2 patients) with healthy volunteers (13.0±0.4 μmol/L) demonstrated an increase in the parameters (p<0.001). The level of homocysteine turned out to be higher in group 1 patients than in those of group 2 (p<0.001). The level of basal insulin turned out to be significantly higher in the studied groups of patients with obliterating atherosclerosis of lower limb arteries (24.9±4.6 mIU/L in group 1; 8.0±0.7 mIU/L in group 2) than in healthy volunteers (5.1±0.5 mIU/L). Statistically significant (p<0.001) hyperinsulinemia was observed in group 1 as compared with group 2. CONCLUSIONS Hyperhomocysteinemia and hyperinsulinemia are predictors of an unfavourable course of the disease. In a high level of these parameters, one may predict an unfavourable course of obliterating atherosclerosis of lower limb arteries.