SUMMARY
The first British national birth cohort study was initially concerned principally with health at the birth of its sample in 1946. Throughout its first fifteen years it received only short-term financial support, but still managed to undertake ten follow-up data collections and broaden its focus to include educational and cognitive outcomes. Then in 1962, when cohort members were aged 16 years, the Medical Research Council (MRC) agreed to be the principal funder. Over the next twenty years, during the cohort’s adolescence and early adulthood, discussion about the study’s focus was influenced by the funding source, the cohort’s age, the data, current policy concerns, and current thought and innovations in measurement in epidemiology. That period began with pessimism about the study’s future. However, towards the end of the twenty years, the MRC review of options for continuation revealed new epidemiological questions on mental health and ageing that required life course data. Consequently the study was continued, and extensively revised health outcome indicators and methods of data collection were first used at age 36 years. They provided new baselines against which to measure future health change with age, and new outcomes with which to test life course effects of hypothesised earlier life exposures, experiences and health. This paper shows how the focus of the study was changed and developed by internal and external pressures and influences between 1962 and 1982, when the cohort was aged 16 to 36 years.