The efficacy of magnesium sulphate in chronic obstructive pulmonary disease (COPD) was assessed by conducting a systematic review of published randomized clinical trials through extensive searches in MEDLINE and SCOPUS with no date limits, as well as manual review of journals. Outcome measures varied depending on route(s) of administration of magnesium sulphate and medications co-administered. Risk of bias was evaluated and quality of evidence was graded. Four (4) randomized trials were included. All trials had a moderate risk of bias and were of average methodological quality. Magnesium sulphate given intravenously did not seem to have an immediate bronchodilatory effect; however it appears to potentiate the bronchodilatory effect of inhaled beta-2 agonists. Increase in peak expiratory flow rate (PEFR) at 30 and 45 min was greater in those who received magnesium sulphate compared to placebo (P = 0.03), although the mean percentage change in PEFR was just 24%, without significant differences in dyspnoea scores, hospital admission rates, or emergency department readmission rates compared to placebo. Nebulized magnesium sulphate with salbutamol versus nebulized salbutamol with saline placebo showed no significant differences is forced expiratory volume in 1 s (FEV 1 ) measured at 90 min after adjustment for baseline FEV 1 (P = 0.34) or differences in the need for hospital admission. Combined inhalational and intravenous magnesium sulphate versus intravenous saline placebo and nebulized ipratropium bromide were comparable in terms of hospital admission, intubation and death, but the ipratropium bromide group showed better bronchodilator effect and improvement in arterial blood gas parameters. Overall, trial evidence for trial evidence for magnesium sulphate in acute exacerbation of COPD is poor, and further well-designed trials are needed.