2-Arachidonyl glycerol (2-AG) exhibits cannabinoid agonist activity at the central cannabinoid (CB1) receptor, is an important endogenous monoglyceride species, and is thus considered to be the natural ligand for the CB1 receptor{5306,6819}. 2-AG can also be metabolized by COX-2 to form prostaglandin (PG) 2-glyceryl esters.{11045} These 2-glyceryl esters rapidly equilibrate to form 90:10 mixtures favoring the more stable 1-glyceryl ester. 17-phenyl trinor PGF2? serinol amide is a stable analog of PGF2? 2-glyceryl ester incorporating an activity-enhancing 17-phenyl substitution. The biological activity of 17-phenyl trinor PGF2? serinol amide has not yet been determined.