Uncontrolled studies suggest that magnesium sulphate controls spasms in patients with established tetanus. We performed a meta-analysis of controlled trials that compared magnesium sulphate with placebo or diazepam for the treatment of patients with tetanus. We searched PubMed, Scopus, Embase and the Cochrane clinical trials registry. Three studies met the inclusion criteria, containing 275 participants (199 male patients, 72.4%). Magnesium sulphate did not reduce mortality, relative risk (95% CI): vs placebo, 0.80 (0.41�1.58); vs diazepam, 1.11 (0.70�1.75). The data on duration of total intensive care unit stay, total hospital stay and the need for ventilatory support were conflicting and pooling of results could not be done due to methodological differences of individual trials. More controlled trials are needed to assess the effect of magnesium sulphate on reducing autonomic instability, spasms, duration of intensive care and hospital stays and the need for mechanical ventilation.