Objectives.To evaluate if the prooxidant environment present in atherosclerotic plaque may oxidatively modify filtered albumin.Methods.Fluorescein-5-maleimide labelled plasma samples and plaque extracts from 27 patients who had undergone carotid endarterectomy were analysed through nonreducing SDS-PAGE for albumin-Cys34oxidation. Furthermore, degree and pattern of S-thiolation in both circulating and plaque-filtered albumin were assayed.Results.Albumin filtered in the atherosclerotic plaque showed higher levels of Cys34oxidative modifications than the corresponding circulating form as well as different patterns of S-thiolation.Conclusions.Data indicate that the circulating albumin, once filtered in plaque, undergoes Cys34oxidative modifications and demonstrate for the first time that albumin is a homocysteine and cysteinylglycine vehicle inside the plaque environment.