A series of (carboxyalkyl)benzyl propargyl ethers was synthesized and tested as inhibitors of 12-lipoxygenase (12-LO) from porcine leukocyte cytosol. Optimum activity was displayed by 3-[4-[(2-tridecynyloxy)methyl]phenyl]propanoic acid. Altering the length of the alkyl side chain attached to the acetylenic group reduced activity. Changing the substitution pattern in the (carboxyalkyl)benzyl group from para to meta or ortho also reduced activity. Analogs in which the triple bond was replaced by a double bond or an allene displayed reduced activity, whereas fully saturated analogs were inactive. High concentrations (10 microM) of the most potent acetylenic (carboxylalkyl)benzyl ethers did not inhibit human platelet 12-LO, human neutrophil 5-LO, rabbit reticulocyte 15-LO, or soybean 15-LO. Thus, this class of compounds represents the first example of isoform specific LO inhibitors.