BACKGROUND:?Cholelithiasis is a common entity in China, but its etiology and pathogenesis have not been fully elucidated. Pigment stones of the intrahepatic and extrahepatic bile duct still form a high proportion in China, while they are rare in Europeans. To date, reports on fatty acids in stones remain few. We analyzed the quantity of fatty acids in different stones from Chinese and Japanese cases and discussed the role and mechanism of fatty acids in the formation of pigment stones. METHODS:?Clinical data from 18 Chinese and 37 Japanese patients with different types of stones were analyzed using the procedure for extracting fatty acids from gallstones and high performance liquid chromatography. RESULTS:?The total fatty acid and free fatty acid contents of pigment stones were markedly higher than those in black or cholesterol stones. The ratio of free saturated to free unsaturated fatty acids was highest in intrahepatic and less in extrahepatic pigment stones, which were signiifcantly different from the other two kinds of stones. CONCLUSIONS:?This indicates that phospholipase participates in the course of pigment stone formation. The action of phospholipase A1 is more important than phospholipase A2.