Each year, an estimated 50 million persons in the United States experience injuries that require medical attention. A substantial number of these persons are treated in an emergency department (ED) or a hospital, which collects their health-care data for administrative purposes. State-based morbidity data systems permit analysis of information on the mechanism and intent of injury through the use of external cause-of-injury coding (Ecoding). Ecoded state morbidity data can be used to monitor temporal changes and patterns in causes of unintentional injuries, assaults, and self-harm injuries and to set priorities for planning, implementing, and evaluating the effectiveness of injury-prevention programs. However, the quality of Ecoding varies substantially from state to state, which limits the usefulness of these data in certain states. This report discusses the value of using high-quality Ecoding to collect data in state-based morbidity data systems. Recommendations are provided to improve communication regarding Ecoding among stakeholders, enhance the completeness and accuracy of Ecoding, and make Ecoded data more useful for injury surveillance and prevention activities at the local, state, and federal levels. Implementing the recommendations outlined in this report should result in substantial improvements in the quality of external cause-of-injury data collected in hospital discharge and ED data systems in the United States and its territories.