A multistage adaptive testing (MST) design was implemented for the Programme for the International Assessment of Adult Competencies (PIAAC) starting in 2012 for about 40 countries and has been implemented for the 2018 cycle of the Programme for International Student Assessment (PISA) for more than 80 countries. Using examples from PISA and PIAAC, this article addresses the advantages and considerations of an MST design in the context of international large-scale assessments (ILSAs). It illustrates and discusses the unique features of the implemented designs in PISA and PIAAC and the expected gains in test efficiency and accuracy, as well as limitations and challenges of MST designs for cross-country surveys. Practical aspects and insights into utilizing MST to measure complex constructs in cross-cultural surveys are provided.