Urinary tract infections continue to be a major health problem for women. Understanding of the pathogenesis of urinary tract infections has improved; Staphylococcus saprophyticus has been recognized as a common causative agent, and low-colony-count infections are misdiagnosed less often. Traditional therapy with 10 days of amoxicillin (Amoxil, Wymox) or ampicillin (Omnipen, Totacillin) is no longer considered optimal. For women who fulfill certain clinical criteria, short-course therapy is recommended--preferably 3 days of trimethoprim-sulfamethoxazole, or trimethoprim alone (Proloprim, Trimpex) if the woman is allergic to sulfonamides. Longer therapy is indicated for women with complicated, prolonged, or recurrent infections. To appropriately treat patients and avoid overtreatment that would increase both costs and the incidence of side effects, physicians need to stay abreast of information about pathogens, mechanisms of disease, new drugs, and common resistance patterns.