The same questionnaire and study design was used in two surveys of asthma among all the children attending the 9-y compulsory school in Sundsvall in 1985 (n = 10527) and 1995 (n = 9165). A detailed questionnaire was distributed by post to the parents of all children who had answered in the affirmative to a simple screening question on asthmatic symptoms at the beginning of the autumn term. The questionnaire contained detailed questions on symptoms and asthma management. Our findings indicated a moderate increase in reported asthma-like symptoms and physician-diagnosed asthma between 1985 and 1995. The severity of symptoms was unchanged, despite a large community-based asthma campaign and a tenfold increase in the number of children receiving inhaled steroids. A validation analysis included an interview by a physician, a skin prick test, determination of specific IgE antibodies and spirometry. The oral interviews suggested that undertreatment was common. Many children had adequate medication at home, but this medication was not used properly. Finally, all 13-14-y-old children also replied to written and video questionnaires from the International Study of Asthma and Allergies in Childhood (ISAAC). It is likely that differences in study design explained the much higher prevalence of wheezing in this part of the study.