EDHF (endothelium-derived hyperpolarizing factor) is an unidentified mediator released from vascular endothelial cells in response to acetylcholine and bradykinin which is distinct from the NOS- (nitric oxide) and COX-derived (prostacyclin) vasodilators. Cytochrome P450 (CYP450) metabolism of polyunsaturated fatty acids, produces epoxides such as (±)14(15)-EpETrE which are prime candidates for the actual active mediator. However, the CYP450 metabolites of eicosapentaenoic acid and docosahexaenoic acid have been little studied relative to arachidonate epoxygenase metabolites. (±)14(15)-EpETE is the ω-3 homolog of 14(15)-EpETrE, derived via epoxidation of the 14,15-double bond of EPA. The EDHF activity of (±)14(15)-EpETE has not yet been determined.