Helicobacter pylori is the etiologic agent of human gastritis and peptic ulceration and produces urease as the major protein component on its surface. H. pylori urease is known to serve as a major virulence factor and a potent immunogen. Recombinant H. pylori urease expressed in E. coli was purified by simple purification procedures utilizing (CNBr-activated Sepharose-anti-urease IgG immunoaffinity chromatography or epoxy- activated Sepharose-urea affinity chromatography. Urease was apparently bound so tightly to the anti-urease IgG resin that it could not be eluted at various elution conditions except at certain extreme pH 1, including 100 mM carbonate (pH 10.5) buffer solution, which was shown to elute slightly inactivated but relatively pure enzyme. Urease eluted from the epoxy-activated Sepharose-urea affinity column showed higher activity, but the smaller UreA subunit of the enzyme appeared as a Fainter band of diminished intensity when subjected to SDS-polyamide gel electrophoresis.