It has been acknowledged that there are many mistakes in recording the casualty variables on the police accident report forms. This study shows how a computer-based linkage of police and hospital records can be used routinely to identify the mistakes for the variables of casualty age, gender, and severity. The level of omissions and misidentifications were 0.4% for gender, 12.2% for severity, and 15.7% for age. The number of records that had age omitted or coded incorrectly was not significantly greater for seriously injured casualties than for those who were slightly injured. This system could be effectively used to code casualty severity using medical information instead of police judgement.