Objective: To investigate the correlation between the expression of nerve growth factor (NGF) and tissue injury in irradiated rat submandibular gland. Methods: The salivary gland regions of the rats were irradiated with a single dose of 15 Gy X-ray. The histopathological changes in the submandibular gland were observed, while the expression of NGF was determined by immunohistochemistry and real-time PCR. Results: The weight of the body and submandibular gland decreased in the irradiated rats 30 days after irradiation, compared with the control group. There were also significant histopathological changes in the submandibular gland of the irradiated rats compared with the non-irradiated rats. The acinar cells and ducts were degenerated obviously. Fibrosis appeared around the ducts. The mRNA and protein expression of NGF in the submandibular gland decreased in the irradiated rats compared with the control group. Protein expression of NGF was even observed in the striated duct in the irradiated rats. Conclusion: NGF may play an important role in protection of the submandibular glands of rats from radiation. Keywords: ionising radiation, nerve growth factor, submandibular gland