13(S)-HpODE is produced by the oxidation of linoleic acid by LO-1 in many plants including soybean, flaxseed, apples, and tea leaves, and by 15-LO in mammals. In plants, 13(S)-HpODE is the preferred substrate for the garlic bulb divinyl ether synthase. In mammalian tissues, 13(S)-HpODE is generally reduced to 13(S)-HODE, a compound which exhibits many biological activities. A direct action for 13(S)-HpODE has been demonstrated in Syrian hamster embryo cells where it stimulates EGF-dependent mitogenesis and up-regulation of EGF-dependent tyrosine phosphorylation. Membrane-esterified 13(S)-HpODE has been identified in human atherosclerotic plaques.