AbstractFatty acids in human and rat adrenal lipids were analyzed by AgNO3‐impregnated silica gel, thin layer chromatography and gas liquid chromatography (GLC). In human adrenal cholesterol ester, 26 kinds of fatty acids were estimated. The percentage of 18∶1 was highest, and 20∶3ω6 and 22∶4ω6 represented high percentages in polyenoic acids. Docosatrienoate was found in all the five men, representing from 1.0% to 2.8%. Its retention time on GLC was different from that of 22∶3ω9 found in the adrenal cholesterol ester of fat deficient rats. The methyl esters of dicarboxylic acids produced by KMnO4‐oxidation of the docosatrienoate had a chain of 10 carbon atoms. These results elucidate that the docosatrienoate from human adrenal cholesterol ester belongs to the linoleate family. In the adrenal cholesterol ester of 10‐week fat free rats, the percentages of 22∶4ω6 and 22∶5ω6 did not decrease, compared with control rats, though arachidonate apparently decreased. The adrenal phospholipid contained about 20% of arachidonate in four of five men and about 40% of arachidonate in rats. Much more polyenoic acids were found in the triglyceride of an adrenal adenoma of primary aldosteronism than in the adjacent adrenal tissue, shereas the fatty acid compositions of phospholipid and cholesterol ester in the adenoma resembled those in the adjacent tissue.