Frailty, the loss of physiologic organ reserve with age, and chronic illness, which may accelerate the development of frailty in one or more than one body system, become the dominant determinants of ill-health in those who escape the hazards of early and mid-life. The Compression of Morbidity paradigm holds that if the average age at first infirmity, disability, or other morbidity is postponed, and if this postponement is greater than increases in life expectancy, then average cumulative lifetime morbidity will decrease, squeezed between a later onset and the time of death. The National Long-Term Care Survey, the National Health Interview Survey, and other data from the United States and some other developed countries now document declining disability trends beginning around 1982 and accelerating more recently. The decline in disability is about 2% per year, contrasted with a decline in mortality rates of about 1% a year, documenting compression of morbidity in the United States at the population level. Longitudinal studies now link good health risk status with long-term reductions in cumulative lifetime disability; those with few behavioral health risks have only one-fourth the disability of those who have more risk factors, and the onset of disability in those with good health habits is postponed from 7 to 12 years, far more than any increases in longevity. Randomized controlled trials of health enhancement programs in senior populations have shown a reduction in health risks, improved health status, and decreased medical care utilization. Health policy initiatives now being undertaken have the promise of increasing and consolidating health gains for seniors under the umbrella paradigm of the Compression of Morbidity.