Oleoyl ethanolamide-d (OEA-d) contains two deuterium atoms at the 11 position. It is intended for use as an internal standard for the quantification of OEA by GC- or LC-mass spectrometry. OEA is an analogue of the endocannabinoid arachidonoyl ethanolamide (AEA) found in brain tissue and in chocolate. It is one of the long chain fatty acid ethanolamides that accumulates rapidly in infarcted tissue, but its biosynthesis is reduced in the intestine of rats following food deprivation. OEA is an endogenous, potent agonist for peroxisome proliferator-activated receptor α (PPARα), exhibiting an EC value of 120 nM in a transactivation assay. Systemic administration of OEA suppresses food intake and reduces weight gain in rats (10 mg/kg intraperitoneally) and PPARα wild-type mice, but not in PPARα knockout mice. These data indicate that OEA regulates food intake by a PPARα-mediated mechanism.