Health care value, quantified as outcome per unit cost, requires knowing which outcomes are influenced by which intervention at what cost. The value of rehabilitation is still largely unknown. Much of the reason for this limited evidence is historically poor standardization and collection of rehabilitation interventions, and objectively measured outcomes across care settings, care providers, and health care systems. The purposeful standardization and aggregation of rehabilitation-relevant data about interventions, cost, and outcomes from routine clinical practices offers potential to understand and improve the value of rehabilitation. This perspective details the critical need for rehabilitation-relevant data that is aggregated across settings, providers, and systems and proposes 3 options to meet this need, including 1) integrating rehabilitation-relevant data into existing research registry databases that are condition-specific, 2) adding rehabilitation-relevant data to federally funded research networks, and 3) creating a novel rehabilitation registry database. There must be continued pursuit of discovering which rehabilitation interventions achieve which specific outcomes, in which settings, for which patients, and at what costs. Successfully aggregating rehabilitation-relevant data is critical for generating evidence that answers these key questions about the value of rehabilitation.