Seventy-nine severe limb injuries were retrospectively reviewed to compare the AO/ASIF and the Gustillo classifications. Specifically, the suitability of these classifications with respect to prognosis and management of these cases was compared. A healed and stable wound was the ultimate outcome measure. Surrogate outcome measures used were: the time to healing; the number of anaesthetics until the wounds were healed; and the number of operations until the wounds were healed. Any change in lifestyle following the injury was also assessed. The primary healing rates of the AO/ASIF groups showed significant (P < 0.001) inter-group differences. However, when the injuries were classified using the Gustillo system, the primary healing rates did not show any differences between the groups. Also, differences in the other outcome measures were most pronounced when using the AO/ASIF system. Importantly, changes in lifestyle correlated with the injury score when using the AO/ASIF system (P < 0.05). Unlike the AO/ASIF system, the Gustillo system was not applicable in 100% of cases. A modified AO/ASIF scoring system is proposed which provides a good predictor of outcome.