Of 146 consecutive closed and Grade I open tibia shaft fractures treated with cast immobilization, external fixation, or intramedullary rod fixation during a 4-year period, 44 of 76 (58%) tibias of patients who smoked and 59 of 70 (84%) tibias of patients who did not smoke had followup to union or followup beyond 1 year. The demographics, fracture patterns, and treatments of the two groups were similar. Two of the 44 patients who smoked had nonunions at the 1-year followup, whereas none of the patients who did not smoke had nonunions. Of the 103 tibias with complete followup to union, the median time to clinical healing for patients who smoked (269 days) was significantly greater than that of patients who did not smoke (136 days). Likewise, there was a 69% delay in radiographic union in the group that smoked as interpreted by a radiologist blinded to the two groups. Statistical differences in clinical and radiographic healing rates between those who smoked and those who did not smoke were observed for patients receiving intramedullary fixation or external fixation. Statistical differences were not seen in the clinical and radiographic healing of tibias treated with cast immobilization, although tibias of patients who smoked took 62% longer to heal. The current data suggest that tibias of patients who smoke who require treatment with intramedullary nailing or external fixation require more time to heal than do those of patients who do not smoke.