Two series of omega-phenoxy contained acylhydroxamic acids as novel urease inhibitors were designed and synthesized. Biological activity evaluations revealed that co-phenoxypropinoylhydroxamic acids were more active than phenoxyacetohydroxamic acids. Out of these compounds, 3-(3,4-dichlorophenoxy)propionylhydroxamic acid c24 showed significant potency against urease in both cell free extract (IC50 = 0.061 +/- 0.003 mu M) and intact cell (IC50 = 0.89 +/- 0.05 mu M), being over 450- and 120-fold more potent than the clinically prescribed urease inhibitor AHA, repectively. Non-linear fitting of experimental data (V-[S]) suggested a mixed-type inhibition mechanism and a dual site binding mode of these compounds.