Programmed death of cells by apoptosis is regarded as a protective mechanism of the organism against an accumulation and spread of defective cells. The rate of apoptosis is elevated in most types of aging cell populations. However, there are also findings about a decreased susceptibility of senescent cells in vivo and in vitro, particularly to apoptosis induced by oxidative and energetic stress. Mitochondria appear to have a key function in apoptosis regulation. Thus, apoptosis can be induced by defective mitochondrial oxidative phosphorylation. The role of apoptosis in aging and age-related disease was outlined for different organs (brain, cardio-vascular system, immune system, intestine, macula of the eye, Langerhans islets, prostate gland, oocytes of ovaries). The age-related intensification of this dismantling system of cells seems to highlight the deterioration of tissue and organ structure and function in aging.