Scotland tested the intelligence of a whole year-of-birth, twice. On 1st June 1932 almost every child born in 1921 took the same general mental ability test. The exercise was repeated on 4th June 1947. These were the Scottish Mental Surveys of 1932 and 1947. They were largely unused between the late 1960s and the late 1990s. Beginning in the late 1990s, our teams of researchers have been following up some people who took part in the Scottish Mental Surveys to conduct studies in cognitive ageing and cognitive epidemiology. Following up the individuals who took part in these surveys and now live in the Edinburgh area—the Lothian Birth Cohort studies of 1921 and 1936—has offered an opportunity to study the determinants of lifetime cognitive ageing differences. This talk will outline how participants of the original surveys were re-contacted, and concentrate on some of the recent results which their follow up has produced. Among the factors that will be considered with respect to people’s differences in cognitive ageing will be social, health, fitness, brain imaging, and genetic factors.