A number of 17-phenyl trinor prostaglandin F2α(17-phenyl trinor PGF2α) derivatives have been approved for the treatment of glaucoma.1,2,3Of these, the ones wherein the 13,14-double bond has been hydrogenated retain relatively good potency, but show a significantly reduced incidence of local irritant side effects.417-trifluoromethylphenyl-13,14-dihydro trinor PGF2αbears an aromatic ring which is reminiscent of the trifluoromethyl-phenoxy ring of travoprost ((+)-fluprostenol isopropyl ester). As an ocular hypotensive agent, it would be expected that 17-trifluoromethylphenyl-13,14-dihydro trinor PGF2αwould act very much like the free acid of latanoprost.