Aim: To evaluate the effectiveness of intravenous magnesium sulphate in the tr eatment of acute asthmatic attacks in children by meta-analysis. Methods: A sys tematic and comprehensive search of the literature was performed to identify con trolled clinical trials of magnesiumsulphate in paediatric acute asthma which ev aluated outcomes of hospitalisation or short term pulmonary function tests or sy mptom scores. Unpublished data were searched by personal contacts with authors a nd specialists. Two reviewers independently assessed trial qualities and synthes ised data. Heterogeneity among studies was evaluated by the Cochrane Q test. Out come data were pooled by random or fixed effect models depending on presence or absence of heterogeneity. Results: Five randomised placebo controlled trials inv olving a total of 182 patients were identified. They compared intravenous magnes ium sulphate to placebo in treating paediatric patients with moderate to severe asthmatic attacks in the emergency department, with co-therapies of inhaled β2 agonists and systemic steroids. The studies were of high quality with results j udged to be valid. Four studies showed that magnesium sulphate was effective, wh ile one study found it ineffective. There was no significant heterogeneity in th e primary outcome of hospitalisation. In the fixed effect model, magnesium sulph ate is effective in preventing hospitalisation (OR 0.290, 95%CI 0.143 to 0.5 89). The number needed to treat is 4 (95%CI 3 to 8). Secondary outcomes of shor t term pulmonary function tests and clinical symptom scores also showed signific ant improvement. Conclusion: Intravenous magnesium sulphate probably provides ad ditional benefit in moderate to severe acute asthma in children treated with bro nchodilators and steroids. Aim: To evaluate the effectiveness of intravenous magnesium sulphate in the tr eatment of acute asthmatic attacks in children by meta-analysis. Methods: A sys tematic and comprehensive search of the literature was performed to identify con trolled clinical trials of magnesium sulphate in paediatric acute asthma which ev aluated outcomes of hospitalisation or short term pulmonary function tests or sy mptom scores. Unpublished data were searched by personal contacts with authors a nd specialists. Two reviewers independently assessed trial qualities and synthesized is data. Heterogeneity among studies were evaluated by the Cochrane Q test. Out come data were pooled by random or fixed effect models depending on presence or absence of heterogeneity. They were intravenous magnes ium sulphate to placebo in treating paediatric patients with moderate to severe asthmatic attacks in the emergenc y department, with co-therapies of inhaled β2 agonists and systemic steroids. The studies were of high quality with results j udged to be valid. Four studies showed that magnesium sulphate was effective, wh ile one study found it ineffective. heterogeneity in th e primary outcome of hospitalization. In the fixed effect model, magnesium sulphate is effective in preventing hospitalization (OR 0.290, 95% CI 0.143 to 0.589). The number needed to treat is 4 (95% CI 3 to 8 Secondary outcomes of shor t term pulmonary function tests and clinical symptom scores also showed significant ant improvement. Conclusion: Intravenous magnesium sulphate may provide ad ditional benefit in moderate to severe acute asthma in children treated with bro nodilators and steroids.