In many jurisdictions, unsafe trucking firms account for a significant number of highway accidents. One way to reduce these accidents is to identify firms with a high potential for accidents and to target them for appropriate safety interventions. Vehicle roadside inspection programmes, such as Roadcheck, can provide an effective means of identifying high-risk trucking firms, based on vehicle-driver fitness rates. This paper makes use of the 1995 Ontario Roadcheck database to establish a link between vehicle roadside inspections aggregated at the carrier level and the carrier accident risk potential in the same year. In Roadcheck, trucks which are selected randomly from the traffic stream passing each inspection station are monitored for a range of mechanical defects, such as brake, suspension system, engine, and tire defects. The focus of this paper is to identify carriers with a high accident risk potential with respect to those accidents which are caused primarily by lack of truck fleet mechanical fitness. Preliminary results suggest that roadside inspections provide a simple, reliable way of establishing a trucking firm's accident risk potential (especially where truck fleet fitness is the central concern). The approach appears to be especially suited as a low-cost screening method for targeting high-risk trucking firms for appropriate safety interventions.Key words: truck, mechanical fitness, carrier, accident risk.