Biliary obstruction induces a increase in the permeability between blood and bile, and a decrease in the rate of immunoglobulin A (IgA) transport into bile. We investigated the effects of percutaneous transhepatic biliary drainage (PTBD) on these derangements. PTBD reduced the extent of elevation of the bile-to-serum ratio of Immunoglobulin G (IgG; IgG-BS ratio) in patients with obstructive jaundice. Because IgG is known to be passively transported from serum to bile, the results indicate that PTBD restores the blood-bile barrier function. The IgA-BS ratio/IgG-BS ratio index (IgA/IgG index) and the IgM/IgG index, which indicated the function of selective transport of IgA and IgM into bile, initially decreased and then returned to the normal range 17 days after PTBD in patients who experienced a rapid resolution of hyperbilirubinemia. However these indices remained low in patients who did not experience this resolution. The serum secretory IgA levels in patients who did not experienced rapid resolution of hyperbilirubinemia markedly increased before PTBD. The serum secretory IgA levels in the patients who did and those who did not experience rapid resolution of hyperbilirubinemia, after initially increasing, decreased after PTBD. However the level returned to the control range only in patients who experienced a rapid resolution. These results indicate that the secretory IgA level is a sensitive indicator of hepatobiliary function, and measurement of the level of secretory IgA could predict the effect of PTBD.