Traumatic brain injury (TBI) is the leading cause of morbidity from trauma in children, and one of the leading causes of death. Despite the frequency of TBI, its impact on the health of children, and decades of research, no effective treatment exists. For adults, however, there have been several recent phase II studies demonstrating the administration of progesterone to those with moderate-to-severe TBI is safe and may have substantial neuroprotective effects. The PECARN conducted a prospective observational yield study to: demonstrate the number of moderate-to-severely brain injured children presenting to PECARN hospitals, determine time of guardian arrival in order to determine appropriate consent methods, and evaluate fesibility of eligibility criteria. Data from this pilot will also allow us to determine how many clinical sites will be required for an interventional trial. Subject enrollment has concluded and a manuscript is in preparation.