Young people who have been in care show relatively poor outcomes in comparison to young people who have not been in care, and run a high risk of social exclusion. Therefore, the transition to adulthood of young people leaving care is an important topic for research. However, there is still little knowledge about the different research approaches and research instruments that are being used in studying this topic. The aim of the present study is to review the approaches and instruments that are used in empirical studies that focus on young care leavers' transitions to adulthood. The results show that the studies apply a diversity of topics and instruments, but that there is also considerable overlap. To make better comparisons on the transition from out-of-home care to adulthood between different countries, a common research framework and one or more research instruments should be developed that can assess this transition and the situation of young care leavers in diverse social contexts.