Background. The therapeutic efficacy of bezafibrate, a hypolipidemic drug, has been shown in patients with primary biliary cirrhosis (PBC) in some pilot studi es; however, little is known regarding the mechanism of action of bezafibrate in PBC. This study was conducted to evaluate the therapeutic efficacy, as well as to gain insight about the possible mechanism of action, of bezafibrate in PBC. M ethods. Sixteen patients ith PBC were administered with bezafibrate (400 mg/day) either with (n =10) or without ursodeoxycholic acid (UDCA; n = 6). The peripher al blood of these patients was collected before and at different times after the rapy commencement, and antigen presentingdendritic cells (DCs) were then culture d. The DCs were enriched and cultured with Staphylococcus aureus Cowan strain-1 for 48 h to evaluate their capacity to produce nitrite.Results. One month after the start of bezafibrate therapy, the serum levels of alkaline phosphatase (P = 0.0005), γ-glutamyl transpeptidase (P = 0.0006), total cholesterol (P = 0.007 2), and immunoglobulin M (P = 0.0281) were decreased significantly compared to t hose before patients started bezafibrate therapy.The levels of nitrite produced by DCs decreased in all patients with PBC within 1 month of commencement of beza fibrate therapy.Moreover, decreased nitrite production by DCs was also seen when nitrite production was evaluated 1 year after the start of bezafibrate therapy. Conclusions. This study reconfirms the therapeutic efficacy of bezafibrate in p atients with PBC,including those with UDCA-resistant PBC. Downregulation of nit rite production by DCs may have some relationship with the therapeutic efficacy of bezafibrate; however, further study will be needed to clarify whether or not the antiinflammatory activity of bezafibrate is mediated through nitrite product ion. Background. The therapeutic efficacy of bezafibrate, a hypolipidemic drug, has been shown in patients with primary biliary cirrhosis (PBC) in some pilot studi; however, little is known regarding the mechanism of action of bezafibrate in PBC. This study was conducted to evaluate the therapeutic efficacy, as well as to gain insight about the possible mechanism of action, of bezafibrate in PBC. M ethods. Sixteen patients ith PBC were administered with bezafibrate (400 mg / day) either with (n = 10) or without ursodeoxycholic The peripher al blood of these patients was collected before and at different times after the rapy commencement, and antigen presenting dendritic cells (DCs) were then culture d. The DCs were enriched and cultured with Staphylococcus aureus Cowan strain-1 for 48 h to evaluate their capacity to produce nitrite. Results. One month after the start of bezafibrate therapy, the serum levels of alkaline phosphatase (P = 0.0005), γ-glutamyl transpeptidase P = 0.0006), total cholesterol (P = 0.007 2), and immunoglobulin M (P = 0.0281) were decreased significantly compared to t hose before patients started bezafibrate therapy.The levels of nitrite produced by DCs decreased in all patients with PBC within 1 month of commencement of beza fibrate therapy. Moreover, decreased nitrite production by DCs was also seen when nitrite production was evaluated as 1 year after the start of bezafibrate therapy. Conclusions. This study reconfirms the therapeutic efficacy of bezafibrate in p atients with PBC, including with UDCA-resistant PBC. Downregulation of nit rite production by DCs may have some relationship with the therapeutic efficacy of bezafibrate; however, further study will be needed to clarify whether or not the antiinflammatory activity of bezafibrate is mediated through nitrite product ion.