One hundred thirty-two open tibial shaft fractures were treated by unilateral external fixation. In order to evaluate the usefulness of supplemental lag screw fixation, we compared forty-four reexamined fractures in which only external fixation was utilized with fifty-five reexamined fractures, stabilized with supplemental lag screws and external fixation. We did not find significant differences in time to full-weight bearing (17.1 vs. 15.6 weeks), time to union (18.7 vs 18.0 weeks), incidence of delayed union [as defined by time to union over 32 weeks (10.9% vs. 11.4%)], incidence of osteomyelitis (5.4% vs. 4.5%), or incidence of malunion [axial malalignment greater than 5 degrees (12.7% vs. 11.4%)]. Clinically significant differences were found demonstrating a twofold increase in refracture rate in the group with supplemental lag screws (10.9% vs. 4.5%) and requiring twice as many bone grafting procedures to achieve union (65.5% vs. 29.5) than did the group treated by external fixation alone. Therefore we do not recommend the routine use of supplemental lag screw fixation.