A hospital-based registration of traffic accident casualties was introduced in Gothenburg in 1979. The purpose was to compensate for the deficiencies in the official traffic accident statistics, to study the mechanisms of injuries in specific accidents in order to facilitate diagnosis and therapy for the injured and to evaluate the effect of protective equipment for vehicles and road-users. This presentation will describe the methods used, present the results obtained so far, and show how data reported by the police and the hospitals can complement each other in a comprehensive analysis of the causes and consequences of traffic accidents.