The past two decades have seen an impressive expansion of literature on the diagnosis, prognosis, and pathophysiology of severe traumatic brain injury (TBI). Rigorous investigations have uncovered the value of standardized bedside assessment, utility of advanced neurotechnologies, and the potential for recovery in even the most severely injured patients. Along the way, we have learned lessons related to the complexity of data acquisition, analysis, and interpretation in this unique patient population. This session will present key findings on assessing level of function and outcome in patients with acute and chronic severe TBI as well as strategies that new studies are implementing to address the limitations of prior research.