The results of gerontological research today are based on cohorts that were born and lived through historically unique circumstances. People now entering old age have had different socioeconomic living conditions and different lifestyles. In Sweden today, people aged 55–64 are much better educated and more likely to participate in political and cultural activities, compared to previous cohorts. They are more likely to have a good cash margin and are less likely to report having economic hardship in childhood. They are more active and have better teeth. On the other hand, they report more physical symptoms and women in this age group are more likely to smoke while men less so. This chapter will use nationally representative longitudinal data stretching from 1968 to 2000 to compare birth cohorts at mid-life in regards to living conditions, activity participation, and health behavior. We will then follow-up the older birth cohorts to examine associations between socioeconomic and lifestyle factors with mortality and disability in late life. Can we assume that the nature of these associations will be similar for all cohorts? And if so, to what extent can we expect improvements in future cohorts of old people?