The International Study of Asthma and Allergies in Childhood (ISAAC) aims to understand the prevalence and severity of asthma, rhinitis, and eczema in children worldwide. The study was initiated to standardize research methods and facilitate international collaboration. It has three phases: Phase 1 involves core questionnaires to assess disease prevalence; Phase 2 investigates potential causes; and Phase 3 repeats Phase 1 to track trends. The study targets children aged 6–7 and 13–14 years, using standardized questionnaires for data collection. The goal is to compare disease prevalence across countries and identify risk factors. ISAAC includes collaborating centers worldwide, with data collected through parent/child questionnaires. The study also includes additional modules for cough, medical care, and physical exams. Data management involves computer entry and analysis, with results shared internationally. The study aims to provide a framework for further research into the causes of asthma and allergies, including genetic, environmental, and lifestyle factors. The ISAAC Steering Committee oversees the study, with regional and national coordinators managing local activities. The study has been widely adopted, with data collected from multiple countries, and is expected to contribute significantly to understanding the global burden of childhood asthma and allergies.The International Study of Asthma and Allergies in Childhood (ISAAC) aims to understand the prevalence and severity of asthma, rhinitis, and eczema in children worldwide. The study was initiated to standardize research methods and facilitate international collaboration. It has three phases: Phase 1 involves core questionnaires to assess disease prevalence; Phase 2 investigates potential causes; and Phase 3 repeats Phase 1 to track trends. The study targets children aged 6–7 and 13–14 years, using standardized questionnaires for data collection. The goal is to compare disease prevalence across countries and identify risk factors. ISAAC includes collaborating centers worldwide, with data collected through parent/child questionnaires. The study also includes additional modules for cough, medical care, and physical exams. Data management involves computer entry and analysis, with results shared internationally. The study aims to provide a framework for further research into the causes of asthma and allergies, including genetic, environmental, and lifestyle factors. The ISAAC Steering Committee oversees the study, with regional and national coordinators managing local activities. The study has been widely adopted, with data collected from multiple countries, and is expected to contribute significantly to understanding the global burden of childhood asthma and allergies.