Oxidative Stress in Aging: From Model Systems to Human Diseases discusses the role of free radicals in aging in different animal models, as well as the relevance of free radicals on age-related diseases and pathological conditions in humans (following an introduction section of the basics and theory of free radicals). Human aging is a complex phenomenon - not everyone gets the same diseases and dies from the same cause. Accumulating reports implicate the connection between free radicals and various diseases and age-related pathological conditions. Although the causal relationships have not been established, it is necessary to discuss how free radicals are involved in each situation. In addition, the major interventions trials of antioxidant supplements in age-related disease, cancer and so forth are reviewed and discussed.