We survey the recent literature on the effects of retirement on cognitive functioning at older ages around the world. We describe results from studies using similar data, definitions and methods to capture causal effects. The studies yield widely varying results. Most papers find that being retired leads to a decline of cognition. However, the size and significance of the estimated effects vary dramatically depending on methods. We replicate several of these results using the same data sets. We discuss the factors that are likely causing the differences observed, and find that results are sensitive to the inclusion of “country effects”, suggesting a key role for unobserved differences across countries that affect both retirement ages and cognitive decline.