CONTEXT: Transforming Growth Factor ß1 (TGFß1) plays a fundamental role in fibrogenesis, although its importance as a biomarker of liver disease is still matter of debate. OBJECTIVE: Quantify serum TGFß1 and its association to liver collagen content in rats exposed to Carbon Tetrachloride (CCl4). METHODS: Rats were submitted to a fibrosis model using CCl4 and sacrificed after 6, 10, 12 and 16 weeks of treatment. Serum levels of TGFß1 were measured by ELISA and collagen content was defined by morphometric analysis. RESULTS: Serum levels of TGFß1 increased between 6 and 10 weeks, whereas collagen density increased between 12 and 16 weeks. A negative correlation was observed between liver collagen deposition and serum levels of TGFß1 (r = -0. 48; P<0. 05). CONCLUSION: Serum levels of TGFß1 were inversely proportional to collagen intensity in cirrhotic livers of rats exposed to CCl4, thus suggesting a limited use as biomarker in advanced liver disease.