The potential benefits to health of the supply of antioxidants, either through dietary intake or as supplements, is equivocal. There is a need to develop biomarkers that may act as monitors of cellular defense as influenced by antioxidant status. Thirty-two individuals participated in the project and 19 received supplements for 5 weeks in the form of a capsule containing a defined mixture of antioxidants. No change was noted in levels of superoxide dismutase and glutathione peroxidase following antioxidant supplementation. On the other hand, increase in total antioxidant status and decrease in malondialdehyde, protein carbonyl formation, and erythrocyte hemolysis were noted. In lymphocytes isolated from individuals receiving antioxidant supplements and subjected to a heat shock in the presence of the free radical generator 2, 2'-azobis-(2-amidinopropane)-dihydrochloride, enhanced synthesis of heat shock proteins hsp 105, hsp 90, hsp 70, and hsp 40 by contrast with decreased synthesis of heme oxygenase HO-1 (hsp 32) were noted. We conclude that antioxidant status modulates the synthesis of stress proteins.