Compressing the period of infirmity into an ever-shorter period between the onset of morbidity and death might reduce the nation's illness burden; for this to occur, age-specific incidence of morbid states must decrease more rapidly than age-specific mortality rates. Recent data demonstrate that the onset of some major chronic illnesses is now being postponed and that increases in females' life expectancy have slowed. Large randomized controlled trials have shown an impact of primary prevention on morbidity exceeding that on mortality. These and other trends provide evidence for some degree of current compression of morbidity and suggest types of public health strategies required for further progress, including successful aging programs.