Between January 1989 and September 1991, 117 consecutive open tibial shaft fractures were treated at our institution. Of these, 64 (55%) met the inclusion criteria and were prospectively treated according to protocol using unreamed interlocking intramedullary nails as definitive fixation. Wounds were classified according to the method of Gustilo et al., and included 10 type I, 16 type II, and 38 type III (17 type IIIA, 21 type IIIB) wounds. Contraindications to intramedullary nailing included (a) fractures involving the proximal or distal one fifth of the tibia, (b) patients with open physes, and (c) an associated vascular injury (type IIIC). Proximal locking was routinely performed, whereas distal locking was used as needed for axial and/or rotational stability. Soft-tissue coverage was obtained after adequate debridement within 7 days: 26 of 64 fractures (41%) required a soft-tissue procedure (17 split-thickness skin grafts, eight free-tissue transfers, one rotational muscle flap). Patients were encouraged to bear full weight in a short leg cast or Sarmiento brace as soon as other injuries or pain permitted. Average follow-up time was 24.8 months (range 12–44) and was possible in 46 fractures (71.875%; nine of 10 type I, 12 of 16 type II, 10 of 17 type IIIA, and 15 of 21 type IIIB). Mean time to healing was as follows: type I, 4.8 months; type II, 4.7 months; type IIIA, 8.28 months; and type IIIB, 9.30 months. Twenty fractures exhibited a delay in healing (>6 months). This included two of 12 type II (16%), six of 10 type IIIA (60%), and 12 of 15 type IIIB fractures (80%). Nine received no treatment, five underwent exchange nailing with a reamed nail, and six were bone grafted. All but one went on to uneventful healing. There were no malunions in either rotation, angulation, or length. Clinically, patients complained of only occasional pain. All had full range of motion of the knee and ankle unless associated with other pathology. Complications included one bent nail and 12 broken screws in 10 fractures (15%). There were six acute infections (13%), all in type III fractures (one IIIA, five IIIB). Two of these patients developed chronic osteomyelitis requiring saucerization; both had type IIIB fractures. Our data indicate that unreamed tibial nailing is an acceptable technique for use in all open tibial shaft fractures (excluding type IIIC). Our overall chronic infection rate was 4%, with no chronic infections in types I, II, and IIIA open fractures and a 13% rate in type IIIB open fractures. In addition, this series was not associated with any malunions. Although delayed union was prevalent, it appeared to be related to the amount of soft-tissue stripping and nail stiffness. The fact that all but one fracture healed with excellent alignment and a minimal infection rate makes this technique suitable for the stabilization of open tibial shaft fractures.