Basic hemostasis and fibrinolysis parameters have been analysed in the group of 35 patients with obliterative atherosclerosis and in 41 patients with diabetes mellitus treated with intra-arterial ozone in concentration of O2/O3 54 micrograms/cm3 O3. Assayed parameters were within normal values. However, a tendency to decreased blood coagulation following ozone therapy was more pronounced in patients with obliterative atheromatosis, than in these with diabetes mellitus.