Concepts of health and homeostasis are discussed and their connection to longevity is analyzed. Homeostasis is one of cardinal properties of the organism, which arises in evolution basing on mechanisms maintaining stationarity. Health represents the organisms' ability to sustain homeostasis and return to it after action of external disturbances. Maintaining the health of a human determines longevity. The factors affecting the health, aging and longevity are discussed. Potential reserves of longevity are estimated and possible ways to achieve them are provided.