[영문]ONE OF THE most notable achievements of modern societies is a large rise inhuman longevity. Since 1800 life expectancy at birth has doubled from about40 years to nearly 80 years. Recent mortality trends are well established,but there is considerable disagreement among demographers and biologistsabout what lies ahead. Pessimists believe we are approaching limits to lifeexpectancy, while optimists expect continued rapid improvements with nolimits. Much is at stake: improvements in longevity are a key cause of skyrocketingcosts of pensions and healthcare for the elderly.After a brief review of the controversy about future trends, this studyexamines past trends in the components of life expectancy at birth. Theprojection of these components provides the basis for assessing plausiblefuture trends in longevity. The focus throughout is on high-income countrieswith low levels of mortality.