Exacerbations of asthma are episodes that require a change in treatment. Treatments of exacerbations are planned gradually according to the needs of the patients. Magnesium sulphate (MgSO4) -either intravenous (IV) or nebulised-is a treatment option that is used with increasing frequency in patients with severe exacerbations of asthma who do not respond to the initial treatment. MgSO4 may have bronchodilatory and an anti-infl ammatory eff ects in the airways. Both nebulised and IV forms of MgSO4 seem to be eff ective in children. However, the effi cacy of nebulized MgSO4 is limited in adults. IV MgSO4 can be used in adults who suff er from a severe exacerbation and who do not respond to the initial treatment. MgSO4 has no major side eff ects and is a cost eff ective treatment that benefi ts patients in addition to the conventional treatments in severe exacerbations. In this review, the role of MgSO4 in exacerbations of asthma was presented with the data obtained from the recent studies and meta-analyzes.