Urease is a virulence factor for the Gram-positive urinary tract pathogen Staphylococcus saprophyticus. The susceptibility of this enzyme to chemical inhibition was determined using soluble extracts of Staph. saprophyticus strain ATCC 15305. Acetohydroxamic acid (Ki = 8·2 μg ml−1 = 0·106mmol l−1) and DL-phenylalanine hydroxamic acid (Ki = 21 μg ml−1 = 0·116mmol l−1) inhibited urease activity competitively. The phosphorodiamidate fluorofamide also caused competitive inhibition (Ki = 0·12 μg ml−1= 0·553 μmol l−1 = 0·000553 mmol l−1), but the imidazole omeprazole had no effect. Two flavonoids found in green tea extract [(+)-catechin hydrate (Ki = 357 μg ml−1 = 1·23 mmol l−1) and (−)-epigallocatechin gallate (Ki= 210 μg ml−1 = 0·460 mmol l−1)] gave mixed inhibition. Acetohydroxamic acid, DL-phenylalanine hydroxamic acid, fluorofamide, (+)-catechin hydrate and (−)-epigallocatechin gallate also inhibited urease activity in whole cells of strains ATCC 15305, ATCC 35552 and ATCC 49907 grown in a rich medium or an artificial urine medium. Addition of acetohydroxamic acid or fluorofamide to cultures of Staph. saprophyticus in an artificial urine medium delayed the increase in pH that normally occurs during growth. These results suggest that urease inhibitors may be useful for treating urinary tract infections caused by Staph. saprophyticus.