Eosinophilic inflammation in the airways is important in the pathogenesis of childhood asthma. Serum eosinophilic cationic protein (ECP), a marker of eosinophil activation was measured in 20 asthmatic children and 19 non-asthmatic controls. There was no difference in the socio-demography, passive smoke exposure, urinary cotinine levels and family history of asthma between the 2 groups. The median serum ECP in asthmatic children was 27.0 mcg/L (IQ1 8.8, IQ3 59.0); which was higher than in non-asthmatic controls [5.9 mcg/L (IQ1 3.0, IQ3 11.9), p=0.002]. An elevated serum ECP level can be helpful as supportive evidence in the diagnosis of bronchial asthma in Malaysia children.