We studied the behavior of some biochemical markers of fibrosis, the aminoterminal propeptide of type III procollagen (P-III-P), laminin, hyaluronate and fibronectin, in the sera of patients with primary biliary cirrhosis (PBC). Significant increases were found in serum laminin, hyaluronate and P-III-P and, more important, a significant correlation was found between the histological stage of the disease and serum hyaluronate. This parameter seems to distinguish between early PBC (I and II stages) and advanced disease with fibrosis. Moreover, a correlation between the histological stage and serum levels of both laminin and P-III-P was observed. Serum laminin, however, increases particularly in advanced disease, whereas high levels of sP-III-P are already present in the early stage. Finally, no significant differences were found between the plasma fibronectin levels of patients with primary biliary cirrhosis and those of controls.