OBJECTIVE To evaluate and present our experience using the expandable nail system for the treatment of acute tibial shaft fractures. METHODS Retrospective study. METHODS Two level-1 trauma centers-University teaching hospitals. METHODS Fifty-four consecutive patients were treated by this nail system for acute tibial shaft fracture. Two nail diameters were used, 8.5 mm and 10 mm. Operation, hospitalization and healing times, reaming versus nonreaming, isolated versus multiple injuries, and reoperations were recorded and analyzed statistically. RESULTS Follow-up was obtained either until fracture healing or for a minimum of 1 year with an average of 14 months (12 to 24). All fractures healed in an average time of 72 days (21 to 204). The average healing times for patients treated with 8.5-mm and 10-mm nails were 77.2 days (27 to 204) and 63.4 days (21 to 121), respectively. Average operative time was 103 minutes (40 to 185) if reamed and 56 minutes (30 to 80) if unreamed. Average healing times were 65.4 days (21 to 190) if reamed and 79.5 days (42 to 204) if unreamed. There were 11 complications (20.4%) related to the nailing: 3 deep infections, 2 superficial infections, 2 bone shortenings of 1 cm secondary to nail protrusion in the knee, 1 compartment syndrome, 1 fracture propagation, 1 distal malalignment, and 1 delayed union. Hardware was removed in 6 patients (3 infections, 2 patients' request and 1 protrusion into the knee), and 1 additional patient underwent exchange nailing due to a delayed union. CONCLUSIONS The expandable nail offers the theoretical advantages of improved load sharing and rotational control without the need for interlocking screws. This study demonstrates satisfactory healing and alignment for the treatment of tibial shaft fractures using this device. However, caution must be exercised when using this nail in cases of significant comminution and in cases where the fracture pattern involves the more proximal or distal aspect of the tibial shaft.