Data are currently inadequate to develop, implement, and evaluate injury prevention and control programs in the United States. Information about cause of injury, which is available for fatal injuries, is rarely available for severe nonfatal injuries. Although hospital discharge data systems contain much of the important information needed for injury prevention and control programs, they rarely are coded with information about the external cause of injury (E codes). E-coded hospital discharge data systems are potentially one of the most effective and feasible means available to collect data needed to prevent and control injuries. We recommend that E codes be required elements in hospital discharge data systems, that separate fields for E codes be created, and that E-code definitions and guidelines be developed.