This paper reviews the magnitude and characteristics of the problem of road accidents involving young adults. The magnitude of the problem is considered from the perspective of the contribution of road accidents to mortality and morbidity among young people, relative to other causes. The over-representation of young adults in road accidents is examined to determine the extent to which it occurs as a result of their involvement as drivers, passengers, or as pedestrians. To determine the characteristics of collisions involving young adults, the potential contributory role of alcohol, drugs, and other factors in their collisions is evaluated on the basis of current epidemiological evidence, drawn particularly from studies conducted in Canada. The review examines factors that are related not only to the frequency of collision involvement, but also to the severity of the collision. Although the principal intention of the review is to identify what is known about factors that appear to contribute to accidents involving young adults, an additional purpose is to identify what is not known, and in this context, to suggest, given current methodological and practical limitations, what is capable of being determined in the near term.