In 1993, 4521 schoolchildren in Oslo, Norway, participated in a European study on air pollution and respiratory health. Incorporated in the primary questionnaire were five questions taken from a study performed 12 years earlier on 1772 schoolchildren in the same city. The response rate was 85% in 1993 vs 95% in 1981. The current and cumulative prevalences of doctor-diagnosed asthma in 1993 were 4.2% and 8.0%, respectively, compared to 2.2% (P < 0.01) and 3.4% (P < 0.01) in 1981. Attacks of breathlessness during the last 3 years were experienced by 7.1% in 1993 and 3.3% in 1981 (P < 0.05). Wheezing or breathlessness on exposure to pollen in 1993 and 1981 was reported by 6.1% and 3.7% (P < 0.01), respectively; to animals by 4.0% and 2.8% (P < 0.05); and to exercise by 10.2% and 4.8% (P < 0.01). The prevalence of occasional wheezing and the cumulative prevalence of doctor-diagnosed eczema, urticaria, and hay fever were not significantly altered. To summarize, a higher prevalence of both doctor-diagnosed asthma and symptoms of obstructive airways disease was reported by children attending primary school in Oslo in 1993 than 12 years earlier. No increase was observed in the prevalence of other atopic diseases.