Many authors have recommended delayed conversion to nailing of open tibial shaft fractures which had been treated initially with external fixation. Most authors have agreed that it was safe to first remove the external fixator, temporarily immobilize the limb in a cast or traction to allow for pin tract healing(generally 1 to 3 weeks), and then proceed to nailing. But, as far as we know, there was few data that had proven the time interval for pin tract healing was necessary to decrease the risk of deep infection. The purpose of this study was to evaluate the results of secondary nailing that was done immediately after removal of external fixator in the patients of open tibial shaft fractures. There were 12 males and 1 female with an average age of the 37.2 years(range, 18-64 years). The mean follow up period was 16.7 months(range, 12-23 months). The external fixation had been mainteined for an average of 47.5 days(range, 21-90 days). Indication of conversion to nailing without time interval was abscence of any serous discharge, reddness or local heating around pin-sites and normal range of laboratory data. All 13 fractures had united without additional surgical procedures or major complications such as deep infection. There were three superficial infections controlled with curettage and short period of oral antibiotics. On the basis of the favorable results of this study, we concluded that the time interval for pin tract healing is not an absolute prerequisite for preventing deep infection as far as no pin tract infection is present.