||As a part of the Pollution Effects on Asthmatic Children in Europe (PEACE) investigation, a 10 week panel study was conducted in Oslo, Norway, from December 1, 1993 to February 14, 1994. Of the 180 children recruited, 125 satisfactorily filled out a daily diary for the entire period, in addition to measuring peak expiratory, flow (PEF) twice daily. The children fulfilled the common PEACE selection criteria for having shown symptoms of lower airways disease. In Norway, geographic and climatic considerations led to choosing the control and urban sites slightly differently from other countries. The urban half of the population of school-age children was selected from those living in the city centre at low altitude whereas the control group lived in the regions surrounding the city, at higher elevations, usually above the winter inversion layer. This led to higher concentrations in the urban region as compared to the control, of particles with a 50% cut-off aerodynamic diameter of 10 μm (PM10) (period average of 19.3 vs 11.2 μg.m-3), black smoke (period average of 27.6 vs 13.1 μg.m-3), NO2 (period average of 49.3 vs 20.8 μg.m-3) and SO2 (period average of 12.4 vs 3.4 μg.m-3). The statistical multivariate, autoregressive time-series based analysis showed no consistent adverse relationship between symptom incidence, prevalence, bronchodilator use or PEF and air pollution exposure in children in Oslo. For symptom prevalence, however, some positive correlations were present, indicative of an adverse effect of pollution exposure, especially to SO2. The prevalence of phlegm in the control population was positively associated with exposure to all compounds. PEF showed conflicting results with both negative and positive associations, yet giving an indication of a slight adverse effect of particles and NO/NO2. Most adverse associations of air pollution with health parameters were found in the control population. In conclusion, no clear effects of air pollution could be seen on peak expiratory flow or medication use. The control panel tended to react more strongly to air pollution levels.