This document is the first in a series on the standardisation of lung function testing, edited by V. Brusasco, R. Crapo, and G. Viegi. It provides general considerations for lung function testing, including definitions, patient considerations, contraindications, position, patient details, therapy, subject preparation, laboratory details, hygiene and infection control, and reference values. The document outlines the importance of accurate and reproducible measurements in lung function testing, and discusses the role of technicians in quality control. It also addresses the potential for infection transmission during testing, and provides guidelines for preventing cross-contamination, including the use of disposable in-line filters. The document also discusses the design of lung function equipment, the level of infection risk, and the qualifications required for personnel conducting lung function testing. It emphasizes the importance of consistent procedures and quality control to ensure reliable and accurate results. The document also includes a list of abbreviations and references to supporting literature.This document is the first in a series on the standardisation of lung function testing, edited by V. Brusasco, R. Crapo, and G. Viegi. It provides general considerations for lung function testing, including definitions, patient considerations, contraindications, position, patient details, therapy, subject preparation, laboratory details, hygiene and infection control, and reference values. The document outlines the importance of accurate and reproducible measurements in lung function testing, and discusses the role of technicians in quality control. It also addresses the potential for infection transmission during testing, and provides guidelines for preventing cross-contamination, including the use of disposable in-line filters. The document also discusses the design of lung function equipment, the level of infection risk, and the qualifications required for personnel conducting lung function testing. It emphasizes the importance of consistent procedures and quality control to ensure reliable and accurate results. The document also includes a list of abbreviations and references to supporting literature.