We have carried out a prospective study to determine whether the basic descriptive criteria and classifications of diaphyseal fractures of the tibia determine prognosis, as is widely believed. A number of systems which are readily available were used, with outcome being determined by standard measurements including fracture union, the need for secondary surgery and the incidence of infection. Many validated functional outcomes were also used. The Tscherne classification of closed fractures proved to be slightly more predictive of outcome than the others, but our findings indicate that such systems have little predictive value.