Asymptomatic urinary tract infection (UTI) in adults can be associated with serious sequelae. During pregnancy, it causes pyelonephritis and low-birth-weight deliveries, both of which can be reduced in frequency by treatment of the bacteriuria. This asymptomatic infection is also associated with an increased risk of perinatal fetal death; no beneficial effect of therapy has been observed for this condition, however. Asymptomatic UTI has been associated with excess mortality in adult women in a general community setting and in adults of both sexes in a nursing home. To date, there has been no adequate test of treatment of asymptomatic UTI in these groups. UTIs that result from short-term, indwelling bladder catheterization in acute-care hospitals are also associated with a marked increase (relative odds equal to 2.8) in the risk of dying during the hospitalization. A randomized trial of preventive measures that reduced the risk of catheter-associated UTI demonstrated a decrease in mortality commensurate with the lesser risk of infection. These data suggest that asymptomatic UTI may increase the risk of death under certain circumstances. Additional studies are indicated to confirm the phenomenon, to identify high-risk persons, and to determine whether prevention and/or treatment of asymptomatic UTI reduces these effects.