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%).(ABSTRACT TRUNCATED AT 250 WORDS)