A multicenter, prospective study was conducted to assess the efficacy of an unreamed, double-locked tibial nail for the acute management of open and/or unstable tibial fractures. Seventy-seven acute unstable and/or open tibial fractures in 74 patients were treated from December 1986 to February 1989. Forty fractures were closed and 37 were open; 25% occurred in polytraumatized patients and 39% of the patients had additional fractures. All closed tibial fractures healed at an average of 14.2 weeks; 94.6% of the open tibial fractures healed at an average of 20.1 weeks. There were no infections in the closed tibial fracture group. There were 4 infections among the 37 patients (11%) in the open tibial fracture group, 2 superficial and 2 deep. There were 7 problems intraoperatively (8.4%) with fin deployment: 2 fins bent during nail insertion, 4 fins penetrated the cortex, while 1 set of fins only partially deployed. Difficulty was encountered with proximal screw insertion in one third of the cases. Considering the high energy of these injuries, the treatment of open and/or unstable tibial fractures with an unreamed, double-locked tibial nail can offer the surgeon a high rate of union (97%) with minimal complications. The low infection rate found in this series indicates that this nail may be of particular benefit in the treatment of closed and select open tibial fractures.