13-S)-hydroxyoctadecadienoic acid -13-S)-HODE) is a 15-lipoxygenase metabolite of linoleic acid produced in endothelial cells, leukocytes, and tumor cells. The biological effects of 13-S)-HODE include inhibition of tumor cell adhesion to the endothelium at concentrations around 1 uM, and down regulation of IRGpIIb/IIIa receptor expression. 13-S)-HODE methyl ester is a neutral, more lipophilic form of the free acid that can been used as an analytical standard for 13-S)-HODE.