Adult stem cell therapy has been proposed for brain injury in young children. While there have been no clinical trials in the US, the therapy is widely advertised and anecdotally reported in multiple internet sources, leading families to seek the treatment in uncontrolled circumstances. The purpose of this review is to present a discussion of the various types of stem cell preparations, with emphasis on adult stem cells, the scientific basis of their development, and the available experimental evidence for their utility in childhood brain injury. We will also provide background information on the biologic events occurring in injured immature brain, as they relate to the transplantation of stem cells. We will then review our own data from neonatal rodent studies with experimental hypoxic-ischemic brain injury. We have shown that early intracerebral administration promotes improved behavioral outcome in the animals, the formation of new neurons, and the preservation of intrinsic cells. New experiments demonstrate the equality of intracerebral and intravenous transplantation in acute neonatal hypoxic-ischemic injury in rodent. We will speculate on the possible clinical uses of adult stem cells. Our current impression is that the cells have the greatest potential for success when administered soon after an injury. What needs to be done to further the field? The different types of cell preparations should be tested against each other in experimental situations. A suitable model of chronic brain injury should be utilized for evaluating the benefit of the cells for this purpose. Long term safety of the cells should be confirmed in animal models. Finally, multicenter clinical trials should be conducted in highly controlled protocols.