Fatty acids (FA) of agglutinating foraminifera of two genera, Bathysiphon and Rhabdammina, collected from a depth of 3307-3377 m in the Kuril Basin, Sea of Okhotsk, and adjacent deep-sea waters of the Pacific Ocean, were analyzed. In lipids of two Bathysiphon species, in addition to common FA typical for marine organisms, the uncommon ?4 and ?7 monoenoic acids and ?4,7-dienoic acid were found in noticeable amounts. FA of two Rhabdammina species included also such uncommon acids as ?5,8,11,14-21:4, ?5,8,11,14-22:4, and ?5,8,11,14-23:4, which are homologues to arachidonic acid. High levels of cis-vaccenic and arachidonic acids were typical for lipids of all the studied species. At the same time, we observed a substantial difference in FA composition between members of these two genera. Using GC and GC-MS of FAME, pyrrolidide and DMOX derivatives, the structures of 10 new FA were confirmed: ?4-i-16:1 (1.1-0.6%), ?7-i-21:1 (0.4%), ?7-ai-21:1 (0.3-0.8%), ?4,11-18:2 (0.3-0.9%), ?4,7-20:2 (8.8%), ?7,12-20:2 (0.4-0.6%), ?4,7-21:2 (0.6%), ?7,12-22:2 (6.4-2.1%); ?5,8,11,14-22:4 (1.2-2.0%), and ?5,8,11,14-23:4 (1.7-2.3%). The origin of the new FA and the role of foraminifera FA in deep-sea communities are discussed.