Rackground/Aims: Gal]stones are now considered to be the aggregated expression of a metabo]ic disease of liver (lithogenic bi]e), nucleation (a kinetic event), crystallization in gel matrices (stasis) ;md gallbladder dysmotility (increased residence time). To evaluate the role of biliary deoxycholate and Immunoglobulin (Ig) in the cholesterol lithogenesis. 1) Comparing the biliary Ig (IgG, IgA & IgM) concentrations in patif the CiB at the operatiI]e acicL composition was analyzed using HPLC. Nucleation time was determined hy polarizing niicroscopic observation of cholesterol crystals (daily fc>r 21 days). Results: Hiliary IgG concentration in gallstone group was significantly higher than control group (55.9 I 17.6mg/dL vs 6.9 + 3.3mg/dL, p<0.05) but IgA and IgM concentrations were not different .etween gallstone group a,id control group. Biliary DCA/CA ratio in gallstone group was significantly higher than control group (0.42 + 0.12 vs 0.13 + 0.05, p<0.05). And, nucleation time m gallstone group was significantly shorter than control group (2.8 days vs 2l days, p<0.05). Conclusions: Vatients with cholesterol gallstones have a higher biliary IgG concetration and DC".A/CA ratio. There were I:iverse correlations between nucleation time and IgG concentration and lC!1/CA ratio. J'his study suggests that biliary IgG and DCA may play an important role in the p,thovc.:iesis of cholestero1 ,allstone formation.(Korean J Gastroenterol 1996; 845-852)