The Crash Outcome Data Evaluation System (CODES) is a program facilitated by the National Highway Traffic Safety Administration as a component of its State Data Program. CODES uniquely uses probabilistic methodology to link crash records to injury outcome records collected at the scene and en route by emergency medical services, by hospital personnel after arrival at the emergency department or admission as an inpatient and/or, at the time of death, on the death certificate. CODES is designed to foster and cultivate crash-outcome data linkage for highway safety applications at the State level, supporting State Highway Safety Offices, State Public Health and Injury Prevention Departments, State Emergency Medical Services Agencies, State transportation departments, and other such agencies; and to facilitate participation in NHTSA coordinated multistate studies using linked data at the Federal level. This document is intended to inform traffic safety professionals, from those in CODES programs to those in the agencies they support, as well as all others interested in traffic safety, on best-practice applications available through linked CODES data.