AimTo find cis-11-eicosenoic acid (20:19, EA)-producing micro-organisms. Methods and ResultsWe found EA-producing fungi by screening about 300 fungal strains and identified a major fatty acid accumulated in the Mortierella fungi as EA by means of GC-MS analysis. In particular, Mortierella chlamydospora CBS 529.75 produced a high amount of EA (363mgg(-1) of dried cells) on cultivation at 28 degrees C for 4days and then at 12 degrees C for 3days. In the result of lipid analysis, most of the EA was a component of triacylglycerols, not phospholipids. ConclusionWe found that M.chlamydospora CBS 529.75 was the best producer for the microbial production of EA. Significance and Impact of the StudyEA is beneficial as a raw material for medical supplies and a moisturizing component of cosmetic creams. This is the first report of microbial production of EA.