Thirty 5-week-old male rats were used to discern the local modifications of the growth plate after drilling. A 1-mm wide drill hole was made on the right femur from the intercondylar notch to the diaphysis crossing the growth plate, with the left femur acting as a shamoperated control. Animals were killed in four five-unit groups at 1, 2, 8, and 16 weeks, respectively, after the surgical procedure. Soft tissues were removed and bone length measured. Distal growth plates of both femora were histologically, histomorphometrically, and histochemically histochemically studied. There were no significant differences in length or growth-plate height between drilled bones and their controls. Drill holes were filled by bony trabeculi formed progressively from metaphyses and adjacent cartilage metaplasia. This bone bridge grew wider as time passed after the surgical procedure. These experimental findings suggest that caution should be taken when pinning fractures through the growth plate. Failed attempts can produce permanent epiphysiodesis bridges.