The past year has seen contributions to our understanding of gallstone pathogenesis from epidemiologic data and from studies of bile physical chemistry and the nucleation of cholesterol microcrystals. The importance of biliary bile acids, phospholipid composition, and mucus glycoprotein secretion in stone formation was investigated further, as was the role of biliary calcium, a component of both cholesterol-rich and pigment stones. Finally, more information on the natural history of biliary sludge, a precursor of gallstones, has come to light.