Biochemical investigations carried out in patients with acute thrombophlebitis of the lower limb superficial veins showed that 70% of such patients develop marked changes in blood plasma lipid spectrum, hyperlipidemia. Blood serum lipid spectrum was examined in 19 patients with various forms of acute thrombophlebitis of the lower limb superficial veins and in 17 with varicose disease. Histologic material for morphologic examination (a fragment of the great subcutaneous vein near saphenofemoral anastomosis and of the wall near the thrombus) was collected during surgery. Venous wall fragments were examined under a light microscope for lipid content. The findings did not confirm the expected changes in venous wall in hyperlipidemia analogous with arterial wall changes in atherosclerosis. That is why we may propose that hyperlipidemia, though not directly changing venous wall structure, contributes to thrombogenesis process via other mechanisms.