Objective: The aim of the study was to investigate whether zinc supplementation affects antioxidant status in European middle-aged and elderly people. Design: Multicentre prospective intervention study, randomized, double-blind, placebo-control. Setting: France (Clermont-Ferrand/Theix. and Grenoble), Italy (Rome), Northern Ireland (Coleraine). Subjects: A total of 387 healthy middle-aged (55-70 yrs) and free-living older aged (70-85 yrs) subjects were randomly allocated to three groups: 0, 15 or 30 mg zinc gluconate/d in addition to usual dietary intake during 6 months. Methods: Oxidative stress status was evaluated by measurement of protein oxidation (plasma thiol groups), lipid peroxidation (plasma thio-barbituric acid reactants, TBARS), whole blood glutathione levels, erythrocyte copper/zinc superoxide dismutase activity and plasma antioxidant status (ferric reducing antioxidant power assay), at baseline and after 3 and 6 months. Results: Zinc supplementation did not alter oxidative stress markers and antioxidant defenses in elderly. after 3 or 6 months, except an increase in Cu/Zn superoxide dismutase activity. Conclusions: In apparently healthy free living elderly people, a single zinc supplementation had no effects on oxidative stress status.