The hypothesis of this study is that the onset of rapid bronchodilatory effect of inhaled Formoterol (12 microgram) is comparable to that of inhaled salbutamol (200 microgram) i.e., the difference in mean forced expiratory volume in 1 second (FEV1) between the 2 groups at 1, 5, 10, 30 and 60 minutes will be less than 10% in children between 5-15 years with mild acute exacerbation of asthma.