Blood and plasma viscosity, total lipids, triglycerides, total cholesterol, free fatty acids, fibrinogen, lipid-gram, and hematocrit were determined in 53 patients with occlusive arteriosclerosis in the lower limbs prior to and after ozone therapy. At the same time the distance of the intermittent claudication was measured. A significant prolongation of the distance walked painlessly, reduction in blood and plasma viscosity as well as the decrease in total cholesterol after therapy with ozone correlated with a decrease of the blood viscosity.