The purpose of this study was to clarify the reaction of the nerve cells at dorsal root ganglion (DRG) during gradual nerve elongation on a genetic level by investigating expression of Interleukin-6 (IL-6) mRNA. IL-6 mRNA at the DRG was analyzed because IL-6 indicated nerve damage. The rat’s femur was gradually elongated to 20mm at the rate of 0.5 mm/day (Slow group), 1.0 mm/day (Middle group), 2.0 mm/day (Fast group) and 20.0 mm/day (Acute group). IL-6 mRNA in bilateral L4-6 DRG was analyzed utilizing RT-PCR and Southern blotting. Toluidine blue stain was performed to examine morphological change of elongated nerve. IL-6 mRNA expression was detected in all groups. IL-6 mRNA was the lowest induction in the Slow group and the highest induction in the Acute group. Additionally, IL-6 mRNA was detected in the control side of the Middle and Fast groups but not the Slow and Acute groups. In the Slow, Middle and Fast groups, there was no degeneration in the axons nor retrograde reaction in the DRG. In the Acute group, there were degenerated myelin fibers and nuclear eccentricities in the DRG. The expression of IL-6 mRNA is considered to reflect repairing nerve damage by gradual nerve elongation. In the Slow, Middle and Fast groups, IL-6 mRNA was induced in spite of morphologically normal. The results suggested that gradual nerve elongation damaged to nerve cell body on a genetic level. It was interesting that the Middle and Fast groups which caused moderate nerve damage stimulated the induction of IL-6 mRNA in the contralateral side. This result suggests that gradual nerve elongation might increase the nerve regenerating capacity on the other side of lengthening. This phenomenon, which did not appeared in the Acute group, was peculiar to gradual nerve elongation.