The aim of this study was to investigate the behaviour of circulating ET-1 in patients with carotid atherosclerosis, before and after carotid thromboendarterectomy (TEA), to test the hypothesis that plasma ET-1 decreases after removal of atherosclerotic lesion. Plasma immunoreactive ET-1 levels were determined in 17 patients with symptomatic and/or hemodynamically significant carotid atherosclerosis on the day before TEA, 48 h and 72 h after surgery and, in 11 of them, also after 8 h and 24 h. Compared to controls, ET-1 levels were significantly higher both before and after TEA; after carotid revascularisation (8 h) ET-1 increased; then, from the 24th h, ET-1 gradually decreased and at the 48th h and 72th h the decrease was significant in front of basal values. The increase of plasma ET-1 in the acute postoperative phase may reflect the degree of surgical stress and manipulation in diseased blood vessels; the following decrease may indicate the improvement of vascular dysfunction in the involved carotid site; the persistence of high ET-1 levels 72 h after surgery could suggest the presence of residual ischemia in the involved district and/or the involvement of other sites in ET-1 production.