Oxidative stress during aging of Saccharomyces cerevisiae in stationary culture was documented by demonstration of progressive increase in the formation of superoxide, decrease in the content of acid-soluble thiols and of acid-soluble antioxidant capacity of cell extracts, and accumulation of aldehydes and protein carbonyl groups in two yeast strains and decreases in activities of antioxidant enzymes. Cells of a CuZn-SOD (superoxide dismutase)-1-deficient strain showed a higher loss of viability than cells of an isogenic wild-type strain. Cell survival was augmented, and changes in biochemical parameters were ameliorated, by addition of exogenous antioxidants (ascorbic acid, glutathione and melatonin) in both strains.