LITTLE information is available on the total fatty acid composition of pasture grass lipids. Shorland1,2 reported that the fatty acids of the acetone-soluble lipids of cocksfoot grass and of rye grass grown in New Zealand comprised about 3 per cent of the dry-matter of the grass; ester-fractionation analysis showed that saturated acids (mostly palmitic) accounted for less than 20 per cent of the total acids and that the remaining unsaturated acids consisted largely of linoleic and linolenic acids. Details were not given of the analysis of the fatty acids of the acetone-insoluble lipids (phospholipids), though it was stated1 that those from cocksfoot grass resembled the fatty acids of the corresponding acetone-soluble lipids, except for a somewhat lower mean unsaturation of the C18 unsaturated components. In earlier work Smith and Chibnall3 isolated the phospholipid fatty acids of cocksfoot grass and showed that they consisted mainly of linoleic, linolenic and saturated components. Contrary to the assumption hitherto made that the acetone-soluble lipids of forage grasses are mainly triglycerides, plus unsaponifiable matter, Weenink4 has recently shown that about 60 per cent of this lipid fraction of New Zealand grasses consists of galactosyl glyceryl esters of fatty acids, largely linolenic acid.