Background Chronic inhalation of air pollutants may causebronchoconstriction, bronchiolitis, and edema of airway, thus alterlung volume. To measure the lung volume, a simple lung functiontest, the peak expiratory flow rate (PEFR), can provide a feature oflung volume in liters/minute.Objective The purpose of this study was to measure PEFR val-ues of primary school children in a high air pollution level area(Medan) and compare the results with the PEFR values of those ina low air pollution level area (Tebing Tinggi).Methods A cross sectional study was conducted on primary schoolchildren (10-12 years of age) during May-July 2000 in Medan andTebing Tinggi. Data were obtained by questionnaires. Physical ex-amination included age, sex, height, weight, and PEFR value. PEFRvalues were measured by Mini Wright peak expiratory flow meter(MPFM) from three blows. The highest volume was taken as thePEFR value. Statistical analysis was done by t-test and p<0.05was considered significant.Results There were 212 primary school children eligible for thisstudy; 107 came from the high air pollution level area and 105from the low air pollution level area. The PEFR values did not dif-fer significantly between the two groups (p>0.05)Conclusion PEFR values in a high air population level area werenot statistically different compared with those in low air pollutionlevel area