The fountain of youth has always been a myth for mankind. Aging is a physiologic state in which a progressive decline of organ functions is accompanied with the development of age-related diseases. The causes of aging remain unknown, probably being related to a multifactorial process. To date, the free radical and mitochondrial theories seem to be the 2 most prominent theories on aging and have survived the test of time. Such theories claim that oxidative stress within mitochondria can lead to a vicious cycle in which damaged mitochondria produce increased amounts of reactive oxygen species, leading in turn to progressive augmentation in damage. If aging results from oxidative stress, it may be corrected by environmental, nutritional and pharmacological strategies. This review summarizes the role of free radicals and oxidative stress in developing aging in kidney and human pathologies.