This article reviews clinical and experimental evidence as to whether magnesium sulfate, administered soon before premature birth, can reduce the high rate of cerebral palsy in tiny infants. Three observational studies have reported an association of magnesium sulfate with lower rate of cerebral palsy, whether treatment was for maternal preeclampsia or for tocolysis. One of these studies also noted a significant reduction in cognitive disability. In another study, no significant protective effect was seen except in a small subset of infants. Magnesium was neuroprotective in many but not all of a variety of experimental studies and has a variety of biologic effects that might account for benefit. All existing clinical studies had relatively small numbers of very premature infants. Although all attempted to control for possible confounders, such studies cannot provide definitive answers as to possible benefits or risks of magnesium therapy. Only randomized clinical trials are likely to resolve the question of whether a brief exposure to an agent which, in the American experience, is considered safe if administered with appropriate supervision, can reduce longterm neurologic disability in premature infants.