What is important for citizens to know and be able to do? The OECD Programme for International Student Assessment (PISA) seeks to answer that question through the most comprehensive and rigorous international assessment of student knowledge and skills. The PISA 2015 Assessment and Analytical Framework presents the conceptual foundations of the sixth cycle of the triennial assessment. This revised edition includes the framework for collaborative problem solving, which was evaluated for the first time, in an optional assessment, in PISA 2015. As in previous cycles, the 2015 assessment covers science, reading and mathematics, with the major focus in this cycle on scientific literacy. Financial literacy is an optional assessment, as it was in 2012. A questionnaire about students’ background is distributed to all participating students. Students may also choose to complete additional questionnaires: one about their future studies/career, a second about their familiarity with information and communication technologies. School principals complete a questionnaire about the learning environment in their schools, and parents of students who sit the PISA test can choose to complete a questionnaire about the home environment. Seventy-one countries and economies, including all 35 OECD countries, participated in the PISA 2015 assessment.