The fatty acid compositions in the body wall, gonads, and alimentary canal of male and female Stichopus japonicus caught in the Sea of Okhotsk off the coast of Abashiri were analyzed to clarify their characteristics. The fatty acid composition was studied also in konowata sold at the market. The analysis was performed by capillary gas chromatography. Major fatty acids that constituted the lipids of the body wall were iso-C15, C16:0, C16:1n-7, C18:0, C18:1n-7, C20:4n-6, C20:5n-3, C23:1n-9, and C22:6n-3. The fatty acid compositions in various tissues were nearly identical between males and females. Although the fatty acid compositions in the body wall and gonads were similar, they markedly differed from the fatty acid composition in the alimentary canal. The iso-C15, C16:0, and C16:1n-7 levels were very high in the body wall, and the C20:1n-9, C20:4n-6, and C20:5n-3 levels were high in the alimentary canal. A very high monoenoic acid content and the absence of polyunsaturated fatty acids with the exception of icosapentaenoic acid were characteristics of the fatty acid composition in konowata.Keywords: sea cucumber, body wall, gonads, alimentary canal, fatty acid, konowata Lipids in marine products are important nutrient components and are related to their deliciousness in season. Lipids are also an important factor in the deterioration of quality of raw sea foods and seafood products. Therefore, the lipid contents and fatty acid composition in marine products is a matter of interest in food science and nutrition. Sea cucumbers are seasoned with vinegar and eaten raw or are processed into foods such as "konowata" by salting the entrails and gonads, "iriko" by drying the muscles, and "kuchiko" by drying the gonads.Some types of sea cucumbers are known to contain considerable quantities of fatty acid C23:1 (n-9), which is absent in other marine animals . A new fatty acid, 7-methyl-6-octadecenoic acid, has also been discovered (Carballeira et al., 1996). The fatty acid compositions of sea cucumbers in markedly different habitats such as coastal regions of the Sea of Okhotsk, which are completely covered by drift ice during the coldest part of the year, are of great interest.There have been a few reports about the fatty acid composition of lipids in the Holothuroidea of the Tropical and Temperate Zones (Carballira et al., 1996;Fredalina et al., 1999;Svetashev et al., 1991;Isay & Busarova, 1984;Svetashev & Busarova, 1984;Chang-Lee et al., 1989). Also, the fatty acid composition of lipids of the Stichopus japonicus caught along the Pacific coast of Southern Hokkaido has been analyzed , but there are no studies concerning the fatty acid composition of the Holothuroidea caught in the colder Sea of Okhotsk.Thus, we evaluated the lipid contents and the fatty acid composition in the body wall, alimentary canal, and gonads of male and female sea cucumbers caught in the Sea of Okhotsk. We also studied fatty acid compositions of salted and matured entrails of sea cucumbers (konowata), and compared them with those of raw sea cucu...