Abstract: Objective To observe the distribution and location of TGF-β₁ in different stages of experimental lesions and to discuss its potential function.Methods Thirty Wistar rats were established experimental periapical lesions in maxillary first and second molar as experimental group while mandibular molar as control group, and they were divided into ten groups by the time（1，2，3，4，5，6，7，8，9, and 10 weeks）after pulp exposure, three rats in everygroup. Expression of TGF-β₁ was detected by histopathology and immunohistochemistry.Results Strong expression of TGF-β₁ was observedin acute inflammation of pulp (1st-2nd week) and periapical tissue (4th-6th week), and idisappeared in pulp aecrosis and in chronic inflammation of periapical tissue(7th week). The main cells expressing TGF-β₁ were macrophage，lymphocyte and fibroblast. Conclusion TGF-β₁ has the certain function in inflammation and prevention of experimental periapical lesions.

Key words: periapical periodontitis