Life expectancy in the UK improved dramatically during the twentieth century. Whether more recent generations are also living longer in good health has serious implications for healthcare systems and the economy. Drawing on evidence from British birth cohort studies following people born between 1946 and 2000-02, we reviewed how physical and mental health have changed across post-war generations. We found little evidence for improving health across successive cohorts when compared at the same age. For several outcomes-particularly obesity, mental ill health, and diabetes-prevalence of poor health was higher in more recent generations, a pattern we term 'generational health drift'. There was little suggestion of improvements in health for cohorts born since 1946. More research is needed to understand the drivers of this trend, which has itself probably been shaped by changing exposure to preventable social and environmental risk factors experienced across the life course.