Asymptomatic bacteriuria is common. Populations with structural or functional abnormalities of the genitourinary tract may have an exceedingly high prevalence of bacteriuria, but even healthy individuals frequently have positive urine cultures. Asymptomatic bacteriuria is seldom associated with adverse outcomes. Pregnant women and individuals who are to undergo traumatic genitourinary interventions are at risk for complications of bacteriuria and benefit from screening and treatment programs. Although screening is recommended for renal transplant recipients, the benefits for these patients are less clear. For other populations, including most bacteriuric individuals, negative outcomes attributable to asymptomatic bacteriuria have not been described. Treatment of asymptomatic bacteriuria in these patients is not beneficial and, in fact, may be associated with harmful outcomes, such as increased short-term frequency of symptomatic infection, adverse drug effects, and reinfection with organisms of increased antimicrobial resistance. Screening for asymptomatic bacteriuria and treatment is recommended for only selected groups where benefit has been shown. Many research questions still need to be addressed. Different populations have unique risk factors, and the benefits and risks of different management approaches for asymptomatic bacteriuria must continue to be addressed systematically in appropriate clinical trials.