The expression of tissue factor (TF) and plasminogen activator inhibitor (PAI)-1 was induced in cultured human umbilical vein cells (HUVEC) by very low density lipoprotein (VLDL). VLDL had a strong capacity for augmenting the expression of TF and PAI-1, while the capacity of LDL or high density lipoprotein (HDL) in this regard was very weak. VLDL and LDL also elevated TF activity in monocyte culture medium (VLDL, LDL) and the conditioned medium markedly elevated TF and PAI-1 production in HUVEC compared with directly added lipoproteins. These findings indicated that lipoproteins affect both monocyte-macrophages and endothelial cells, and that they cause a hypercoagulable-hypofibrinolytic state. It is thus possible that hyperlipidaemia could be a direct risk factor for thrombotic disease even if atherosclerotic lesions are not present.