It is desirable to have a single MDI that can be used as both LABA and SABA. There are few studies involving few children on use of formoterol that shows rapid bronchodilatation in children with asthma and no study that used it as rescue drug in children with acute exacerbation of asthma. The purpose of the present study is to evaluate whether the rapid bronchodilatory effect of formoterol is similar to that of salbutamol in children of 5-15 years with mild exacerbation of asthma.