Asymptomatic bacteriuria is common in both the community nursing home and hospital settings. Few data, however, are available about the potential complications arising from asymptomatic bacteriuria (eg, the development of symptomatic infection and renal damage) for various patient populations and for various medical conditions. On the basis of data in the literature, we believe that neonates and preschool children with asymptomatic bacteriuria should be treated. Pregnant women and "nonelderly" (less than 60 years old) men should be treated. We do not think that school-age children, nonpregnant, nonelderly women, or elderly men and women need antimicrobial treatment if their urinary tracks are normal. In addition, antimicrobial treatment is recommended for patients with asymptomatic bacteriuria and abnormal urinary tracts and those undergoing clean intermittent catheterization, genitourinary manipulation, or instrumentation. Patients with long-term indwelling catheters should not be treated. The treatment of asymptomatic bacteriuria in patients with short-term indwelling catheters and those with ileal conduits is controversial. These treatment recommendations should not necessarily be accepted as the standards of practice, since treatment is often controversial due to the lack of published data describing the natural course of asymptomatic bacteriuria in various patient populations.