Recently interlocking intramedullary nailing is used widely for the management of tibial shaft fractures. We evaluated any differences in healing time and complications associated with reamed and unlearned tibial interlocking intramedullary nailing. Between January 1991 and February 1996 we performed a retrospective trial on 62 patients with tibial shaft fractures comparing the reamed with unlearned interlocking nailing. The mean time to union for patients with unlearned intramedullary nail was 18.5 weeks(13 to 32 weeks) which was significantly less(P<0.05) than the 21.7 weeks(16 to 36 weeks) for reamed group. The complications of the reamed interlocking intramedullary nailing were three delayed unions (9.3%), three superficial infections(9.3%), and two cases of knee joint or ankle joint LOM(6.2%). The complications of the unlearned interlocking intramedullary nailing were four delayed unions(13.9%), three angular deformities(10.3%), three screw breakages(10.3%), and one superficial infection(3.4%). Unlearned interlocking intramedullary nailing is better for the tibial shaft comminuted fractures with small diameter, unstable tibial isthmus fractures, pelytraurnatized patient and some type of open fractures.