Magnesium sulfate has become the first-line tocolytic for short-term use to arrest idiopathic preterm labor. The reasons for its acceptance include familiarity of the drug, ease of use, and the virtual absence of serious maternal side effects. Sufficient data exist showing its efficacy if used in higher doses. Attention to treating preterm labor has shifted to seeking answers about the fundamental causes. Gathering information about the specific causes and designing tailor-made treatment protocols for each of the numerous potential causes is essential. Scientifically sound research is needed to obtain answers about the important clinical questions surrounding magnesium sulfate.