Our goal was to study changes in anti-cholesterol antibodies (ACHA) levels in patients with severe carotid stenosis after eversion endarterectomy. Seventy consecutive patients who underwent eversion endarterectomy at the Department of Cardiovascular Surgery, Semmelweis University, Budapest, were included in the study. Serum samples from 66 healthy volunteers served as controls. Patients had medical check up at 5.7 (4.6-8.0) weeks (median (interquartile range)), 6.8 (6.2-7.9) months as well as 13.8 (12.3-19.0) months after endarterectomy. In all patients the carotid arteries were investigated by color duplex ultrasound. ACHA concentrations were determined in the serum samples taken before operation as well as at the first and last follow-up visits by using an ELISA method. ACHA concentrations (median (interquartile range) were found to be significantly (p<0.0001) lower in the sera of the patients with carotid atherosclerosis (13.5 (8.4-21.3)AU/ml) than in the healthy subjects (26.1 (20.9-33.2)AU/ml) (Mann-Whitney test). Strong negative correlation was found between the preoperative ACHA and LDL-cholesterol levels (r=-0.413, p=0.0004). Serum ACHA concentrations significantly (p<0.0001) increased from the values measured before operation (13.5 (8.4-21.3)AU/ml) to 27.1 (19.9-34.7)AU/ml measured at the end of the 14 months long follow-up. Increase occurred only in patients with low or medium baseline ACHA concentration. Our present findings indicate that after surgical removal of atherosclerotic plaques from the carotid arteries the reduced baseline levels of ACHA reach normal values in 1 year. Different not mutually exclusive mechanisms (binding of ACHA to lipid/lipoproteins particles, to advanced plaques or reversibly injured endothelial cells in CNS) can be responsible for this novel finding.