We have reviewed our experiences with prefabricated functional braces in the treatment of diaphyseal tibial fractures. The braces were developed in an attempt to reduce the occasional technical difficulties encountered with the use of custom-made braces. Between January 1979 and July 1983 we treated 625 diaphyseal tibial fractures. One hundred and eighty-six patients (29.8 per cent) were lost to follow-up, the braces had to be discontinued in thirty-eight (9.2 per cent), and ten fractures (2.5 per cent) failed to unite. We conducted careful radiographic and clinical analyses of the remaining 391 patients. Two hundred and fifty-seven (65.7 per cent) of the fractures were closed and 134 (34.3 per cent) were open. Three hundred and fifty-seven (91.2 per cent) of the patients had ten millimeters of final shortening or less, and 306 (78.3 per cent) had a final angulation of 5 degrees or less. The average time from injury to bracing was 3.9 weeks (range, one to twelve weeks) for the closed fractures and 5.0 weeks (range, one to twelve weeks) for the open fractures. These findings appear to support our concept that function of the extremity is beneficial to osteogenesis and that many diaphyseal tibial fractures can be satisfactorily stabilized in prefabricated functional braces. These braces also have the advantage of not immobilizing the adjacent joints and they permit the gradual restoration of weight-bearing.