Aging is a degenerative process that decreases physiological function of organisms, especially at later stages, being related with some neurodegenerative diseases as well as cancer. The free radical theory states that the targets of reactive oxygen species (ROS) are random, indiscriminate and cumulative. In the present study, using Saccharomyces cerevisiae cells as an experimental model of eukaryotic organism, we investigated the role of Cu-Zn superoxide dismutase  (Sod) in maintenance of chronological lifespan. The antioxidant Sod catalises the conversion of superoxide radicals to oxygen and hydrogen peroxide, which is further eliminated by catalase or other peroxidases. Saccharomyces cerevisiae possesses two isoforms, the cytoplasmic Cu-Zn and the mitochondrial Mn-Sod, which have been shown to play an important role in protection of yeast against oxygen toxicity. Cells growing exponentially on glucose were either directly incubated in water at 37^°C (for accelerating aging process) or previously treated with 0.2 mM H₂O₂ or 0.5 mM menadione (a source of superoxide anions) before being incubated at 37^°C. We also tested cells growing in low glucose concentrations to examine the effects of caloric restriction, an intervention used to slow aging progress in many organisms ranging from yeasts to primates. In the both strains (sod1D and control strain), adaptive treatments with H₂O₂ or menadione increased lifespan. Caloric restriction increased cell longevity in both strains, but after 48 hours the mutant strain showed a lower viability and higher levels of intracellular oxidation and lipid peroxidation than control strain. These results indicate that superoxide dismutase is an important defence against ROS and, consequently of aging process.