AIM: The balance between oxidants and antioxidants can play an important role in the initiation and development of liver diseases. Recently, we have described a new automated method for the determination of total antioxidant capacity (TAC) in human serum and plasma.METHODS: We measured TAC and corrected TAC (CTAC -abstraction of interactions due to endogenous uric acid,bilirubin and albumin) in 52 patients with chronic liver diseases (41 patients with primary biliary cirrhosis (PBC),10 patients with chronic hepatitis C and 13 patients with viral HCV cirrhosis) as well as in 10 healthy controls. In 23 PBC patients measurement were also done 6 mo after treatment with ursodeoxycholic acid (UDCA). The TAC assay was based on a modification of the crocin bleaching assay. The results were correlated with routine laboratory measurements and the histological stage of PBC.RESULTS: There were no significant differences in TAC between the various groups. However, CTAC was considerably increased in the PBC group compared to controls and cirrhotics. Analysis of these patients according to disease stages showed that this increase was an early phenomenon observed only in stages Ⅰ and Ⅱ compared to controls, cirrhotics and patients with chronic hepatitis C).After 6 mo of treatment with UDCA, levels of CTAC decreased to those similar to that of controls.CONCLUSION: Patients in the early stages of PBC present with high levels of corrected total antioxidant capacity and this maybe related to the pathophysiology of the disease. UDCA treatment restores the levels of CTAC to control levels.