The aim of the present study was to investigate if alterations in protein S levels occur in peripheral arterial disease. In a group of 33 patients with peripheral arterial disease and in a group of 10 healthy volunteers we have the quantitative determination of functional protein S. The observer values show non significant difference in protein S levels among vasculopathic patients and controls (only five out of 33 patients showed low protein S levels). These data seem to suggest that low protein S levels do not play an important role in the development of peripheral arterial disease.