Objective: To evaluate the efficacy of intravenous magnesium sulfate for moderate to severe '}slhma in pediatric patients. Design: A randomized. group comparative, single center study. Setting: Emergency Department, Benha Faculty of Medicine, EI Zagazik University. Patients: Thiny three patients, aged 6-14 years old. being suffering from Bronchial asthma and treated for an acute asthma exacerbation. 'lain outcome measures: Peak expiratory flow rate, forced expiratory volume in I second, forced ital capacity. blood pressure, oxygen satumtion, clinical asthma scores and serum magnesium Ieels. Results: At 20 minutes, the time at which the infusion was completed, the magnesium group had a ,ignificamly greater percentage of absolute improvement from baseline in eadl of the following predicted peak expiratory rate (7.44% V5 0.27%, p