The epidemiological aging research has the descriptive task of characterizing the phenomena of aging and their consequences: illness, disability, handicap, and death--in defined population groups and comparing these groups. The other closely related task is analytical epidemiology, which searches for predictive or causal factors: traits, events or conditions of the aging phenomena. Special problems for this research are created by the facts that exposure to the causal factors often may be assumed to have taken place long time before the aging process becomes apparent, that the causal factors may act on cumulative basis over long time, that the effects may be irreversible, and that the factors may no longer play a role at advanced age. The possible role of genetic factors, acting alone or in combination with environmental factors, must be considered and elucidated by special epidemiological methods. The rapid advances in molecular biology raise expectations about epidemiological utilization providing much more precise assessment of the genetic contribution to the aging phenomena, which also will improve the outlook of identification of environmental factors, particularly when there is a gene-environment interaction. The results of these studies will contribute to prevention and treatment of the health problems related to aging.