Eighty four SLE patients have been studied. The levels of Willebrand factor, total antibodies to cardiolipin class IgG, antibodies to D-DNA, total index of inflammatory process activity SLEDAI and other routine markers have been assessed. Endothelial-dependent vasodilatation of brachial artery and carotid intima-media thickness was found to exceed that of control group twice as much. The elevation of Willebrand factor is associated with increase in SLE activity and correlated with SLEDAI index, C-reactive protein level and total antibody content to IgG class phospholipids. The elevation of Willebrand factor activity is also associated with endothelial-dependent vasodilatation impairment in patients with high inflammatory process activity in particular.