OBJECTIVES: Posterolateral bone grafting to treat nonunions of the distal two-thirds of the tibia avoids the often traumatized and more tenuous anterior soft-tissue envelope. Few modern reports of its effectiveness are available. We assessed whether posterolateral bone grafting leads to high union and low complication rates. METHODS: We conducted a retrospective review at a Level I trauma center. Our study group was 59 patients with distal two-thirds tibial fractures treated with posterolateral bone grafting. Patients included those with history of deep surgical site infection (SSI) before bone grafting (n=17), established nonunions (n=42), and impending nonunions associated with open fractures and bone gaps (n=17). All patients were followed for a minimum of 12 months unless they achieved union before that time point. Our primary outcome measurement was fracture union. Secondary outcome measurements were any complication associated with the approach and infection requiring return to the operating room. RESULTS: Fracture union was achieved in 44 (75%) of 59 patients without further intervention. The mean interval to union was 9.9 months (range, 3-22). Of 11 infected nonunions treated, nine progressed to union. Seventeen of 23 patients with defects >2cm, including defects up to 5.4cm without infection, were successfully treated. Two patients who underwent grafting at least 10 years after initial injury achieved union. No complications were associated with the approach (specifically, no wound breakdown, vascular injury, or tendon injury). Fourteen percent of patients experienced SSI after bone grafting. Seven of eight deep SSI occurred in patients with previous infection or positive intraoperative cultures. Only one (3%) of 36 patients without infection pre- or intraoperatively experienced SSI. CONCLUSIONS: Even in this relatively difficult patient cohort that included large bone gaps and history of infection, union was achieved at a relatively high rate with posterolateral bone graft. The approach seems to be safe, considering no known complications specifically associated with the approach occurred, and seems to reduce the risk of SSI in the absence of previous infection.