Severe type III open fractures were subtyped according to the differences in prognosis for sepsis, amputation, and treatment: IIIA (adequate soft-tissue coverage of bone with extensive soft-tissue laceration or flaps), IIIB (extensive soft-tissue loss with periosteal stripping and bone exposure), and IIIC (arterial injury requiring repair). Analysis of 303 open fractures revealed a sepsis rate of 0% in type I, 2.5% in type II, and 13.7% in type III. The rate of amputation was 18.7%, and the rate of nonunion was 18.5% in type III open fractures. Type IIIA, IIIB, and IIIC open fractures had sepsis rates of 5%, 28%, and 8%, and amputation rates of 2.5%, 5.6%, and 25%, respectively. The overall wound sepsis rate in the 303 open fractures was 4.4%, and the nonunion rate was 8.6%.