Phase 1 of the International Study of Asthma and Allergies in Childhood (ISAAC) used a standardised protocol to obtain comparable international prevalence data on the symptoms of asthma and the related atopic disorders of allergic rhinitis (hayfever) and atopic eczema. The target sample for each centre was 3000 and the ages studied were 6-7 years (parental questionnaire) and 13-14 years (written and video questionnaire to the children). The questionnaires were translated into the local language.

For the questionnaire to 13-14 year olds, data were obtained during 1991-95 from 155 centres in 56 countries and comprised 463,801 participants altogether. All major regions of the world were represented, though Europe predominated with about half of the centres.