Trauma, which accounts for a substantial part of the morbidity and mortality in 
industrial nations, is a natural area of interest for orthopaedic surgeons. 
Trauma, and trauma prevention, can be conveniently studied in emergency rooms 
and casualty units which are often run by hospital orthopaedic departments. In 
order to identify the most serious types of accidents and assign priorities as 
regards preventive measures it is necessary to be able to determine in an 
objective way the severity of different types of trauma. The Abbreviated Injury 
Scale is a system developed in the United States for ranking the severity of 
specific trauma lesions. This paper discusses general issues relating to injury 
scaling and accident epidemiology research.