Although the free radical theory of aging is widely accepted among scientists, the possibility of using antioxidants to delay the aging processes seems to encounter considerable skeptism among clinicians. This may be, at least in part, due to lack of knowledge about the basic chemistry and biological behavior of oxidative stress, antioxidants, and the complex interactions between them. However, one cannot ignore the explosive growth of information concerning the mechanisms underlying the processes of aging, their consequences, and the use of antioxidants in suppressing such effects. In order to provide patients with the most accurate information regarding the use of antioxidant supplementation in their diet, it is important to obtain basic data regarding oxidative stress and antioxidants. This article explores the role of oxidative stress in the aging phenomena, recent evidence supporting supplementation of antioxidants for aged people,  the ability of antioxidants to prevent or retard cancer and atherosclerosis (the major causes of mortality in the aged population), and the ability of antioxidant supplementation to delay age-dependent deterioration of cognitive function. Based on the data presented, we conclude that current knowledge provides insufficient and inconclusive support for antioxidant supplementation as a means of delaying aging processes, despite the encouraging results obtained in many studies.