Macroenzymes are normal enzymes complexed with an immunoglobulin (usually IgG, rarely IgA or IgM). A number of macroenzymes have been reported in the literature. Among them, macro-AST has been detected in diseases such as acute and chronic hepatitis, various malignancies and autoimmune diseases, but usually not associated with any specific disease. We report a case of elevated AST activity in serum due to marco-AST formation in a female with chronic hepatitis C which was confirmed by AST isoenzyme electrophoresis. To our knowledge, this is the first report of macro-AST occurred in chronic hepatitis patient in Korea.