Biological Theories of Aging Aging rate is the result of genomic and stochastic factors interactions. If organic capacity to face the insults of stochastic factors is insufficient, cell imbalance should income leading to increase susceptibility to accumulate damage, which is patent on cell, tissue and organic aging phenomenon. To understand this phenomenon it’s necessary to recognize the specific biologic mechanisms that underlie these imbalances, and that lead to the progressive age-related deterioration in function, causing an increase in susceptibility to disease, and thereby enhancing the risk of death. Related interest on this problem encourages the development of several biologic theories of aging, some of them supported on genetic factors, and the others focused on the stochastic mechanisms. Some of the most popular biological theories of aging will be reviewed in this paper.