Urease inhibitors are candidate drugs to treat infection with the human pathogen, Helicobacter pylori, which produces a potent urease [urea amidohydrolase; EC 3.5.1.5]. We developed a screening system based on 13C-NMR measurement of the time course of decrease in the signal of 13C-urea in the presence of urease. The effect on urease activity of known inhibitors, hydroxamic acids, L-ascorbic acid, 2,2'-dipyridyl disulfide and ninhydrin, was speedily and conveniently measured by this method.