The mainstream in Leonid and Natalia Gavrilovy’s investigations is the search for longevity factors acting at early stages of human life. For example, young dump men stand considerably less chance to become a centenarian than persons of the same age having thin or normal constitution. Living conditions in early childhood (for example, childhood spent at a farm) also affect longevity. Some factors may be changed only while planning a child. It was found that one of those factors was mother’s age at childbirth. At present, the researchers have started a large-scale project aiming to study longevity in the USA. That project will allow to ascertain more carefully how living conditions in childhood, youth and middle age affect achieving of exceptional longevity (100 years). Besides factors connected to living conditions, Gavrilovy’s project also includes the search for biological factors of longevity using population data — that is the subject of a science called biodemography. Particularly, creation of an extensive database of long-lived Americans (several thousands of people lived till their centenary) will allow to clarify the type and mode of life span inheritance, the influence of parent’s longevity at the pathway of descendants’ mortality. It will also allow to ascertain the role of parents' reproductive age in the achieving of exceptional longevity by their descendants. One of Leonid and Natalia Gavrilovy’s investigations was devoted to different demographic scenarios and population size forecasts. The aim of the investigation was to clarify demographic consequences of the successful biomedical struggle against aging. It led to a very important conclusion which can change current public opinion claiming that life extension obviously results in overpopulation. People born from young mothers (20–25 years) have twice better chance to live till 100 years than people born from older mothers. The researchers found that a victory over aging, joy of contact with children and stable population size are not incompatible.