Purpose: To investigate temporal changes in IL-1${eta}$ mRNA expression in spinal dorsal horn (DH) and dorsal root ganglion (DRG) in a rat lumbar disc herniation (LDH) model. Methods: Autologous nucleus pulposus, harvested from the tail disc between the second and third coccygeal vertebrae (Co2-3), was implanted next to the left L5 nerve root just proximal to the DRG after partial laminectomy. IL-1${eta}$ mRNA expression was investigated in DRG and DH in our LDH model. Real-time PCR assays were done using a 7500 Real Time PCR system (Applied Biosystems, USA). Results: Expression of IL-1${eta}$ in DRG and DH was observed for 30 days postoperatively. Expression of IL-1${eta}$ mRNA in the ipsilateral DRG of the LDH group gradually increased from 5 to 30 days after surgery. The amount of IL-1${eta}$ in the contralateral DRG peaked 10 days after surgery and then gradually decreased. However, there was no difference in IL-1${eta}$ mRNA expression in spinal DH between the LDH group and the sham-operated group. Conclusion: Long-term expression of IL-1${eta}$ in the LDH model may worsen the chronic pain state. Future studies on inhibition of IL-1${eta}$ expression in the LDH model will be needed to develop selective treatment strategies for patients with LDH.