Student engagement is of central importance in a low-stakes assessment such as OECD Programme for International Student Assessment (PISA). In the theoretical section, this report provides an overview of the literature on the topic and identifies sources of information to compute measures of disengagement in PISA. In the empirical section, the consistency, associations with student variables, and stability over time are examined for a set of measures based on data from PISA 2018, 2015, and 2012. The various measures investigated only show little consistency, an exception being rapid guessing on the test and non-response in the questionnaire. Boys, socio-economically disadvantaged students, as well as students with an immigrant background are more likely to show disengagement. Furthermore, disengagement is consistently associated with lower test performance. The report concludes with a discussion of possible solutions to address the impact of disengagement on the inferences made on the basis of PISA test and questionnaire data.