Background: Magnesium sulfate (MgSO4) is considered to be a well-tolerated, inexpensive, and effective medication for severe asthma exacerbations. We surveyed physicians who treat patients with asthma to evaluate the current knowledge and usage of MgSO4. Methods: A self-administered questionnaire was e-mailed to members of the Turkish National Society of Allergy and Clinical Immunology and was distributed to participants of its annual congress. Results: Of the 456 respondents (mean age: 36.53 +/- 9.11 years), 42.3% reported to use MgSO4 in asthma exacerbations in their practice, and 48.7% agreed that MgSO4 was included in asthma guidelines. The best known indication was that it was useful only in patients refractory to bronchodilators and systemic corticosteroids (67.7%). The two most common reasons to use MgSO4 were to shorten hospital stay (94.7%), and prevent admission to intensive care unit (80.3%). The respondents mostly used MgSO4 in the treatment of severe or life-threatening exacerbations. Thirty-nine percent believed that MgSO4 had no effect on discharge period, and 29% of them marked minor side effects. The most common reason for not using MgSO4 was inexperience (36.5%). Having an academic affiliation (OR=3.20, p<0.001), the number of asthmatic outpatients seen per month (OR=1.82, p=0.007), and more recent graduation from medical school (1991) (OR=0.23, p<0.001) were associated with the use of MgSO4 in the multivariate analysis. Conclusion: Even though the effect of MgSO4 in acute severe asthma is well known, only half of the physicians dealing with asthma patients have used it in their practice. Education and encouragement in this regard are necessary.