A prospective study was undertaken to accurately classify open tibial fractures and to evaluate the benefit of muscle flaps in the management of these injuries. From 191 open tibial fractures, 59 type III and 14 type IV open fractures were identified and managed prospectively. Fractures managed with open-wound techniques have a much higher complication rate than those closed with flaps. Results with flap coverage are affected by the biologic phase of the wound. The best results are seen in the acute flap coverage group and are thought to be secondary to removal of devitalized tissue with provision of a vascularized soft-tissue envelope prior to wound colonization. Flap coverage of the colonized subacute wound is subject to invasive infection with additional tissue loss. The subacute wound should be managed with open-wound technique until the parameters of a chronic localized wound are established, at which time flap coverage is again indicated. Microvascular free flaps are the preferred cover for type IV wounds because the local tissues are too ischemic and devitalized for transfer. With meticulous wound care and adherence to the enumerated surgical procedures, limb salvage may be achieved in most injuries.