A series of novel benzoheterocyclic [(methoxyphenyl)amino]oxoalkanoic acid esters has been prepared. These compounds were tested as inhibitors of rat polymorphonuclear leukocyte 5-lipoxgenase (LO) in vitro and as inhibitors of leukotriene D4 (LTD4) and ovalbumin (OA) induced bronchospasm in the guinea pig (GP) in vivo. In general, inhibitory activity against 5-LO, LTD4, and OA was broadest for benzthiazole-containing analogues (benzthiazole greater than benzimidazole much greater than benzoxazole, benzofuran). The most potent 5-LO inhibitor, 4-[[3-(2-benzthiazolylmethoxy)-phenyl]hydroxyamino]-4-oxobutanoic acid methyl ester (7), had an IC50 of 0.36 microM. Compound 7, however, was inactive vs. OA. The most potent compound in vivo, 4-[[3-[(1-methyl-2-benzimidazolyl)methoxy]phenyl]-amino] -4-oxobutanoic acid methyl ester 4, inhibited both LTD4- and OA-induced bronchospasm by 83% and 60%, respectively, at 50 mg/kg intraduodenally. Compound 4 was studied in the Ames assay employing five strains of bacteria (TA1535, TA1537, TA1538, TA98, and TA100) with and without S-9 rat liver enzyme metabolic activation, and there was no significant number of reversions noted.