OBJECTIVE To determine the pathologic significance of Staphylococcus saprophyticus in complicated urinary tract infections. METHODS We performed a retrospective analysis of specimens demonstrating this organism based on a survey of 9980 urine specimens cultured in our clinic during an 11-year period. Forty-two specimens from 34 patients were positive for S. saprophyticus. RESULTS S. saprophyticus was isolated in 13 women without underlying urologic disease, and their symptoms were compatible with acute cystitis or acute pyelonephritis. S. saprophyticus was isolated from 7 men and 14 women with underlying urologic disease. In most of these 21 patients, S. saprophyticus was thought not to be a true uropathogen but rather a colonizer, because the isolated organism was usually low in numbers and found with a low degree of pyuria, and the hosts were usually asymptomatic. However, 2 patients demonstrating S. saprophyticus colonization developed sepsis after urologic surgery. CONCLUSIONS Although this organism is pathogenic in certain circumstances, suggesting the necessity of preoperative antimicrobial elimination, it is usually a colonizer in complicated urinary tract infections.