Many species of bacteria in the genus Staphylococcus show a positive test for the enzyme urease, which catalyzes the degradation of urea to form two molecules of ammonia and one molecule of bicarbonate. Under physiological conditions, the ammonia becomes protonated to form ammonium ions, which raises the local pH and can contribute to the virulence of the bacteria. These bacteria can cause skin, joint, soft tissue, gastric, and urinary tract infections as well as bacteremia. Among the best characterized urease-positive pathogenic species of Staphylococcus are S. aureus, S. cohnii subsp. urealyticum, S. epidermidis, S. leei, S. lugdunensis, S. saprophyticus, S. warneri, and S. xylosus. This review summarizes the properties of these bacteria and describes the native and subunit structures of their urease proteins. Sequence comparisons are used to show the common features of multiple isolates of S. aureus, S. epidermidis, and S. saprophyticus, and to compare the sequences of the urease subunits of these species to those from jack bean (Canavalia ensiformis) and other pathogenic bacteria including Helicobacter pylori, Klebsiella aerogenes, Proteus mirabilis, and Ureaplasma urealyticum. The effects of various chemical and natural product inhibitors on the urease enzymes are described, as is the regulation of their synthesis. This summary demonstrates the key role of this enzyme in these bacteria and suggests further lines of research.