LysoPA(18:1(9Z)/0:0) is a lysophosphatidic acid. It is a glycerophospholipid in which a phosphate moiety occupies a glycerol substitution site. Lysophosphatidic acids can have different combinations of fatty acids of varying lengths and saturation attached at the C-1 (sn-1) or C-2 (sn-2) position. Fatty acids containing 16 and 18 carbons are the most common. Lysophosphatidic acid is the simplest possible glycerophospholipid. It is the biosynthetic precursor of phosphatidic acid. Although it is present at very low levels only in animal tissues, it is extremely important biologically, influencing many biochemical processes. In particular, lysophosphatidic acid is an intercellular lipid mediator with growth factor-like activities, and is rapidly produced and released from activated platelets to influence target cells. 1-Palmitoyl lysophosphatidic acid is the major component of lysophosphatidic acid (LPA) in plasma, and is in a reduced ratio in individuals with gynecological cancers. LPA is a pluripotent lipid mediator controlling growth, motility, and differentiation, that has a strong influence on the chemotaxis and ultrastructure of human neutrophils. In serum and plasma, LPA is mainly converted from lysophospholipids, whereas in platelets and some cancer cells it is converted from phosphatidic acid. In each pathway, at least two phospholipase activities are required: phospholipase A1 (PLA1)/PLA2 plus lysophospholipase D (lysoPLD) activities are involved in the first pathway and phospholipase D (PLD) plus PLA1/PLA2 activities are involved in the second pathway.