Abstract: Objective: To investigate the dynamic expression of TGF- β 1 mRNA and protein at different stages of hepatocellular carcinoma (HCC) development. Methods: Male Sprague- Dawley (SD)rats were used as hepatoma models and were induced with 2- FAA. Morphological changes in rat livers were observed by H&E staining. A fragment of the TGF- β1 gene was amplified by nested RT- PCR.Dynamic changes in the level of TGF- β 1 protein were quantitatively analyzed by ELISA. Simultaneously, the expression and cellular distribution of TGF- β 1 were detected in rat livers by immunohisto-chemistry. Results: Histological examination confirmed the rat hepatocytes progressed from granule-like degeneration to atypical hyperplasia and HCC development after induction with 2- FAA. Following this development, hepatic TGF- β 1 mRNA and protein increased. The mRNA and protein levels in hep-atoma tissues were significantly higher than those in normal tissues (P<0.05). The immunohistochem-istry results indicated the positive expression and hepatocyte distribution of TGF- β 1 in rat hepatoma.Similar to TGF- β 1 mRNA, a trend of increasing TGF- β 1 protein expression was found in precancerous to cancerous tissues during HCC development, and a positive relationship was found between the expression levels of TGF- β 1 mRNA and protein. Conclusion: TGF- β 1 may participate in hepatocyte carcinogenesis. The early expression of TGF- β 1 during HCC development could be a useful molecular marker for early diagnosis and prognosis of HCC.