This chapter of the report from the European Respiratory Society provides a comprehensive overview of lung function tests, focusing on lung volumes and forced ventilatory flows. It is divided into several sections, including an introduction, indices and definitions, methods, and application of tests. The chapter covers static and dynamic lung volumes, their determinants, and the impact of various factors such as stature, age, and body mass on lung function. It also discusses the assessment of restrictive and obstructive ventilatory defects, the measurement of forced vital capacity (FVC), and the interpretation of results. The chapter emphasizes the importance of standardized procedures and equipment to ensure accuracy and comparability in lung function testing. Additionally, it addresses the variability in measurements and methods to reduce errors, as well as the need for quality control and calibration. The chapter concludes with a summary of recommendations for measuring conditions, indices, reference values, equipment, and hygiene.This chapter of the report from the European Respiratory Society provides a comprehensive overview of lung function tests, focusing on lung volumes and forced ventilatory flows. It is divided into several sections, including an introduction, indices and definitions, methods, and application of tests. The chapter covers static and dynamic lung volumes, their determinants, and the impact of various factors such as stature, age, and body mass on lung function. It also discusses the assessment of restrictive and obstructive ventilatory defects, the measurement of forced vital capacity (FVC), and the interpretation of results. The chapter emphasizes the importance of standardized procedures and equipment to ensure accuracy and comparability in lung function testing. Additionally, it addresses the variability in measurements and methods to reduce errors, as well as the need for quality control and calibration. The chapter concludes with a summary of recommendations for measuring conditions, indices, reference values, equipment, and hygiene.