Associations were examined between complexity of main lifetime occupation and cognitive performance in later life. Occupational complexity ratings for data, people and things were collected from the Dictionary of Occupational Titles (DOT) for 1066 (men= 534, women= 532) individuals in the Lothian Birth Cohort 1936. Early life ability is one of the largest predictors of later life cognitive abilities and one of the greatest strengths of the study is the availability of early life ability measures for all participants, which was included as a covariate in the final analyses. Additionally men and women were analysed separately to explore potential gender differences. General linear model analyses indicated that, after correcting for age 11 IQ and social deprivation, complexity with people and data were associated with better cognitive performance at age 70. For women complexity with people exhibited the largest effect sizes in later life cognitive performance. For men complexity with data exhibited the largest effect sizes across the four cognitive domains however, complexity with data was only found to be significantly associated with general cognitive ability scores (‘g’ factor). The results support differential preservation hypotheses, that more stimulating environment throughout a lifetime help to preserve cognitive ability in later life, although the continued effects into old age are still debated. Studies that have early life ability measures are rare and the study offers interesting prospects for future research that may further understanding of successful ageing.