The TIMSS 2019 Assessment Frameworks provide the foundation for the TIMSS assessments. The Mathematics (Chapter 1) and Science (Chapter 2) Frameworks describe the major content and cognitive domains to be tested at the fourth and eighth grades. Chapter 3 provides the Context Questionnaire Framework which describes the home, school, and classroom factors associated with learning in mathematics and science that are investigated via the TIMSS contextual questionnaires. Chapter 4 provides an overview of the assessment design including general parameters for item development.