The multicentre Central European Study of Air Pollution and Respiratory Health (CESAR) aimed to measure the respiratory health of schoolchildren using a standardised questionnaire in six countries of Central and Eastern Europe (CEE), allowing comparisons within this region and with other European countries. A cross-sectional study was conducted in 25 urban areas of Bulgaria, Czech Republic, Hungary, Poland, Romania, and Slovakia in 1996. Parents of 21,743 schoolchildren of age 7-11 yrs completed a questionnaire based on items from the World Health Organization and International Study of Asthma and Allergies in Childhood questions on cough and wheeze symptoms, as well as on diagnoses by doctors. Life-time prevalence of bronchitis was 55.9%, asthma 3.9%, and asthmatic, spastic or obstructive bronchitis 12.3%. In CEE countries the prevalence of bronchitis is higher and prevalence of asthma appears lower than in Western Europe. However, if asthma is defined as a diagnosis of either asthma or asthmatic, spastic or obstructive bronchitis, then its prevalence is comparable to Western Europe, or higher. In this region, within-country variation for most respiratory parameters is less than between-country variation. Between-country comparisons in doctors' diagnoses appear dependent on the choice of definition of asthma. Europe-wide comparisons in prevalence of respiratory symptoms and diagnosis are reported in this study. Some of the East-West difference in asthma prevalence may be attributable to differences in diagnostic practice.